Narrow Results

In this work, we will investigate structural, electronic, magnetic, and thermodynamic properties using density functional theory (DFT) and the quasi-harmonic Debye model. We consider ferromagnetic (FM) and non-magnetic (NM) states for L2₁ and Hg₂CuTi-type crystal structures. The best stability is obtained for ferromagnetic Rh₂MnGa in a Cu₂MnAl structure with a lattice parameter of 6.07 Å and a total magnetic moment of 4.11${\mu }_B$. The compressive strain range from $-6$% to $+4$% tensile strain maintains the ferromagnetic nature and enhances the magnetic moment up to 4.39${\mu }_B$. The formation energy confirms the inherent stability of Rh₂MnGa. Other important thermodynamic parameters such as the expansion coefficient ($\alpha$), heat capacity ($C_V$), Debye temperature (${\theta }_D$) and Grüneisen constant ($\gamma$) are also estimated in this work.

DFT is used for making first-principles calculations of electronic and optical properties of V₂O₅ in its orthorhombic phase, by employing Augmented Plane Waves$+$local orbital method with Generalized Gradient Approximation and Perdew–Burke–Ernzerhof potential to account for exchange–correlation interactions. The stability of the material is checked through the calculation of cohesive energy and Bader charge analysis is done to find out the electronic charges on different atoms in the unit cell. A DOS gap of about 2.1eV and a direct band gap of about 1.85eV just above the Fermi level is found to occur on using DFT, which is lower than the experimental value of 2.77eV. On using the DFT$+$U method, with $U=4.0$eV for Vanadium, a DOS gap of about 2.8eV and an indirect band gap of about 3.0eV are found to occur, which are closer to the experimental result, showing that the DFT+U method better accounts for electronic properties of V₂O₅. The optical properties, such as dielectric function, reflectivity, absorption coefficient, optical conductivity, refractive index, extinction coefficient and electron energy loss function also investigated for V₂O₅ by using DFT.

In this work, we delve into the investigation of the structural, electronic, and optical properties of Ba₂NbBiS₆ and Ba₂TaSbS₆ chalcogenide-based double perovskites, which are structured in the cubic space group $Fm\bar{3}m$ form. We have performed first-principles calculations using density functional theory (DFT) to study the above properties. The electronic band structure and density of states of this compound have been investigated, and their results show that Ba₂NbBiS₆ and Ba₂TaSbS₆ exhibit a semiconducting nature with an indirect energy gap of 1.680eV and 1.529eV, respectively. Furthermore, an investigation was conducted on the optical properties of the compounds throughout the energy range spanning from 0eV to 55eV. This investigation focused on many parameters, including dielectric functions, optical reflectivity, refractive index, extinction coefficient, optical conductivity, and electron energy loss. The optical data obtained from the calculations reveals that all compounds demonstrate isotropy in optical polarization. Furthermore, it has been noted that our compounds exhibit absorption properties inside the ultraviolet (UV) region. Consequently, these materials hold promise as potential candidates for various applications, such as UV photodetectors, UV light emitters, and power electronics. This is primarily attributed to their inherent absorption limits and the presence of prominent absorption peaks in this spectral range. In brief, chemical mutation techniques have been employed to manipulate the characteristics of double-sulfide perovskites to develop durable and environmentally friendly perovskite materials suitable for solar purposes.

This study provides a thorough analysis of magnesium oxynitride (MgON), employing first-principles calculations to investigate its potential for electronic, thermoelectric, and optical applications. The main objective was to comprehend the fundamental electronic, thermoelectric, and optical parameters of MgON using density functional theory (DFT) calculations. In electronic properties, the density of states (DOS) spectra revealed the significant contribution of Mg-s and O-p states for pristine MgO, while N-p states provide the maximum contributions with overlapping at the Fermi level in nitrogen-containing compositions. The band structure depicted a direct nature for undoped and doped MgO, and the bandgap of compositions was observed to decrease with the increment in nitrogen concentration. The thermoelectric properties of pure and N-doped MgO compositions were evaluated, which showed significant variations with an increase in temperature and doping. Furthermore, the optical properties of MgON were inspected and found to enhance optical conductivity, and absorption coefficient, whereas the refractive index and dielectric constant decrease at specific energy regions for elevated dopant content, which suggests its suitability for optoelectronic applications. Overall, this study reveals the versatility of MgON, making it a potential candidate for advanced electronic, thermoelectric, and optical applications.

This paper presents a simulation of the structural and optoelectronic properties of Scandium Arsenide (ScAs) and Aluminum Arsenide (AlAs) compounds. Theoretical modeling was performed using ab initio first-principles calculations, specifically the density functional theory (DFT), and the Mindlab numerical software. The software used two methods: the full-potential muffin-tin orbital method (FP-LMTO) and the full-potential plane-wave method (FP-LAPW). These two methods are employed to solve the Schrödinger equation. The exchange correlation effects have been computed using two different approximations: the generalized gradient approximation (GGA) and the local density approximation (LDA). Our findings indicate that the zinc blende structure (B3) is the stable phase, while the Wurtzite phase (B4) is metastable for the AlAs compound. On the other hand, the ScAs compound crystallizes in the NaCl phase (B1). The AlAs compounds undergo three phase transitions: $\mathrm{\text{B3}}\to \mathrm{\text{B4}}$, $\mathrm{\text{B3}}\to \mathrm{\text{B2}}$ and $\mathrm{\text{B3}}\to \mathrm{\text{B1}}$. In contrast, ScAs does not undergo any transition. The obtained results for equilibrium energies, lattice parameters and gap energies are in closer agreement with the experimental and theoretical data. The AlAs compound exhibits a semiconducting character, while ScAs exhibits a semi-metallic character. Additionally, the refractive index of these two compounds is similar to that of silicon, which is crucial for their application in photovoltaic cells.

In this paper, we present the implementation of the Density Functional Theory (DFT) method using the Geant4-DNA framework in the Single Instruction Single Data (SISD) mode. Furthermore, this implementation is improved in terms of execution time within the GeantV project with vectorization techniques such as Single Instruction Multiple Data (SIMD). Within this framework, a set of SIMD strategies in molecular calculation algorithms such as one-electron operators, two-electron operator, quadrature grids, and functionals, was implemented using the VecCore library. The applications developed in this work implement two DFT functionals, the Local Density Approximation (LDA) and the General Gradient Approximation (GGA), to approximate the molecular ground-state energies of small molecules and amino acids. To assess the performance of the implementations, a standard test simulation was performed in multiple CPU platforms. The SIMD vectorization strategy significantly accelerates DFT calculations, leading to time ratios ranging from 1.6 to 5.4 in either individual steps or entire implementations when compared with the scalar process within Geant4.

The influence of incorporating iron on the electronic structure, magnetic and optical properties of zigzag (10,0) boron nitride nanotubes (BNNTs) was investigated using first-principles calculations. The structures were incorporated with Fe according to B1$-x$Fe xN at various (x) contents (0.10, 0.20 and 0.30). Our calculations exhibited that adding additional Fe atoms reduced the energy gap of the structure. Incorporating more iron atoms creates additional sharp peaks within Fermi levels that come from the contribution of Fe-3d states. Doping with (Fe) also introduced magnetic moments in the BNNT structure. The optical parameters of the Fe-incorporated boron nitride nanotube are calculated. The real part of the dielectric function of pristine BNNT started to increase up to the middle of the UV region and then rapidly decreased between the wavelength range of 310–390 nm. Also, the pure boron nitride nanotube has no absorption in the visible light range and only detects UV radiation. The optical calculations showed that incorporating Fe shifted the absorption peaks of BNNTs into risky UV radiations, which helps researchers develop a vision for controlling and developing advanced materials for various electronic applications.

Investigation electron transport via molecular nanoscale junctions is one of the fundamental steps in developing improved high-performance thermoelectric materials for cooling and converting waste heat into electricity. Density functional theory (DFT) and non-equivalent Green’s function are applied to investigate the electric and thermoelectric properties of Fullerene $({\text{C}}_{60})$ doped with three metalloid ions from the periodic table. The M@C${}_{60}$ (M = P, As and Se) systems have two types of electrodes (gold and graphene). The results show that the electric conductance of G with gold leads is higher than the conductance attached to the graphene leads. Also, ${\text{C}}_{60}$ doped by Se is the best compared with P and as for both gold and graphene electrodes. Moreover, the calculations of HOMO-LUMO resonance shifted toward the high energy (low wavelength) in order $\mathrm{\text{Se}}>\mathrm{\text{P}}>\mathrm{\text{As}}$ due to the electronegativity, which is ordering $\mathrm{\text{Se}}>\mathrm{\text{P}}>\mathrm{\text{As}}$, with the Fano-resonance fixed around E–E${}_F=0$. Meanwhile, the value of Seebeck coefficient S for graphene leads is higher than S linked to the gold lead. Also, the merit figure for ZT and thermal electricity has been investigated.

We carry out a computational investigation of the alkaline-earth (Ba)-based silicon and carbon oxide perovskites (BaSiO₃ and ${\text{BaCO}}_3)$ with the aim of their potential in wide-ranged applications. Exploiting the density functional theory (DFT) coded within Wien2K, we study the structural, electronic, and optical properties of these compounds. Modified Becke–Johnson (mBJ) potential, the established approach for obtaining accurate results, is employed to carry out the electronic investigation. With a simple cubic structure, we find that these materials exhibit metallic properties, as revealed by their mutually consistent band structure profiles and density of states. The valence band minima and conduction band maxima overlap at the $\mathrm{\Gamma }$ point in the band structure. We analyze the total and partial density of states to determine the proportional contributions of each atom, both in total and within individual subshells, such as the $p$- and $d$-subshells in the case of the partial density of states. In our investigation of the optical properties of these materials over the energy range of 0–14eV, we find that they effectively absorb ultraviolet and visible (UV–Vis) light. This shows that the studied compounds have potential applications in luminescence and devices requiring absorption in the UV range. BaCO₃ demonstrates more absorption spectra than the BaSiO₃ versus photon energy ranging from 1.7 to 3.1eV (visible range), suggesting that the BaCO₃ is more suitable than BaSiO₃ for applications that require UV absorption such as sunscreen, UV-blocking films, photodetectors and UV sensors and medical applications. We also find that BaCO₃ with a higher refractive index (11) compared to BaSiO₃ (4.2), is denser than BaSiO₃, resulting in a lower speed of light within the material. This suggests that BaCO₃ is more promising than BaSiO₃ for applications in eyewear. We infer that this study will guide and stimulate experimental investigations into these materials, given their potential for various applications.

Heme-type porphyrins can become distorted depending on their environment, altering their chemical and electronic properties. While trends have been established for several ruffle-distorted porphyrins, their research on synthetic models of heme-type porphyrins is limited. We identified a dynamic process on the ruffled porphyrin bis(2-methylpyridinato)iron(III)-Protoporphyrin-IX (2) that does not exist in bis(pyridinato)iron(III)-Protoporphyrin-IX (1). We modeled these molecules as {OMP(2-CH₃Py)₂Fe}${}^{+}$ and {[OMP](Py)₂Fe}${}^{+}$ respectively. Geometry optimization using density functional theory (DFT) suggests the ruffled conformation of 2 (angle x̄ of $-29.7^{\circ }$) and the planar conformation of 1. The calculated electron affinity and ionization potential vary depending upon ruffling. The calculated 0.253 eV difference in electron affinity and the 0.223 eV in ionization potential indicate that the reduction of the planar structure has a higher energy requirement than the ruffled-distorted structure but has a lower energy requirement for its oxidation. We found that these energy differences are not solely attributed to the distortion of the macrocycle. The difference is linked to the interaction between the d${}_{\text{x}\text{y}}$ orbital and the HOMO-1 3a${}_{2\text{u}}$, allowed by symmetry when a porphyrin ring has a ruffled conformation stabilizing the frontier orbitals, thus making the oxidation process have a higher energy barrier. On the other hand, the reduction process is facilitated by the interaction of metal d_π orbitals with the porphyrin 4e. These highlight the distinct differences between the ruffled and the planar conformations.

The advancement of science and technology is essential for the progress of nanotechnology, which plays a pivotal role in the development of miniaturized and energy-efficient devices. This investigation delves into the As-doped structures within one-dimensional germanene nanoribbons. Utilizing Density Functional Theory (DFT) in conjunction with the Vienna Ab initio Simulation Package (VASP), the study explores the electro-optical properties of the material influenced by As doping, examining both the doping position and density’s effects. Results indicate As significantly alters the electro-optical characteristics, with the semiconductor structure transitioning to metals in top and valley configurations, while meta and para configurations retain semiconductor properties with an indirect band gap. Analysis of bond length, bond angle, magnetism, formation energy and charge density difference elucidates As’ impact on hexagonal structure stability and electromagnetism properties of the system. Furthermore, a comprehensive investigation of optical properties not only offers insights into material systems but also highlights potential applications in optical communications and sensing technologies.

In this paper, we investigated the structural, elastic, topological-electronic properties as well as optical properties of two half-Heusler (HH) heavy fermions-based compounds: HoPtBi and HoPdBi. We accomplished our calculations in the framework of density functional theory (DFT), based on the full potential linearized augmented plane wave (FP-LAPW). Both compounds are antiferromagnetic (AFM) type-II as reported by experimental data so we carried out our study in the AFM type-II configuration. Considering the spin-orbit coupling, we found that the hydrostatic pressure leads to a phase transition from the trivial semimetal to the topological semimetal (TSM) because of band inversion for HoPdBi with no apparent effect of hydrostatic pressure on the topological phase for HoPtBi. We also studied their optical properties, without and with hydrostatic pressure. The first peak in reflectivity, absorption, optical conductivity spectra and energy loss factor are strongly influenced by the hydrostatic pressure. Both compounds exhibit a considerable first absorption peak in the visible and ultraviolet ranges and they are best candidates for solar cells considered essential in renewable energy.

The ground state geometry of the nickel derivative [Daiquiris(nicotinamide-jN1) nickel(II)]-fumarato-K2O1:O4 has been optimized and is being led toward its quantum chemical analysis in this paper. For more accuracy, we used the 6-311$++$G (d, p) basis set for C, H, N, and O atoms and the LAN2DZ basis set for Ni. The calculated and experimental infrared (IR) spectra for the title molecule are well correlated, and the correlation factor $R^2=0.9947$ shows that the method effectively interprets the molecule’s IR spectra. The electronic properties such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and associated energy gap have been calculated by Time-Dependent Density Functional Theory (TD-DFT) approach. The natural bond orbital (NBO) analysis of the molecule describes how interatomic charge transfer results in the formation of bonding–nonbonding interactions. The experimental and calculated Ultraviolet visible (UV-Vis) spectra are compared. We anticipate our work will inspire fresh approaches to the title molecule’s ongoing research.

Monolayer Molybdenum disulfide (ML-MoS₂) has emerged as a promising two-dimensional (2D) material with unique electronic, optical and mechanical properties. In this paper, with the aid of first-principles calculations, we explain the optimization of the structural and computational parameters and discuss the electrical properties of ML-MoS₂. The electronic properties were studied comparatively with and without considering the spin-orbit coupling (SOC) effect that shows, ML-MoS₂ has a direct bandgap. A decrease in bandgap energy by 100 meV and a $k$-valley splitting of 100 mV were observed with the inclusion of SOC. The electronic properties were further analyzed using fat band structures and projected density of states (PDOS), which depict the predominant contribution of Mo $d$${}_x$²${}_{-}$${}_y$², $d$${}_{xy}$ and Mo $d$${}_z$² orbital to the valence band maximum (VBM) and conduction band minimum (CBM), respectively. Strain-induced bandgap variation was also observed due to the deformation of the crystal structures by shifting and splitting of the energy levels.

For quite a long time, the scientific community has been searching for a material that surpasses the existing material systems in terms of energy conversion efficiency for photovoltaic applications. In this study, the optoelectronic properties of pure and Al-doped boron arsenide B${{}_{1-}}_x$Al${}_x$As $(x=0,0.125\mathrm{\text{and}}0.25)$ in the zinc blende (ZB) structure were systematically examined using the density functional theory (DFT) and the Modified Becke–Johnson (TB-mBJ) exchange correlation (XC) potential. The Perdew–Burke–Ernzerhof generalized gradient approximation (PBE) functional was used for structural optimization. After considering the ground state lattice constant of 4.82Å then calculating the bandgap energy of pure BAs, which are consistent with experimental and theoretical findings, we estimated the basic electronic and optical characteristics of Al-doped boron arsenide, including band structures, electronic density of state, dielectric function, refractive index, extinction coefficient, absorption and optical conductivity. The unusual and interesting optoelectronic features of the investigated compounds revealed in this work offer substantial promise for improving the energy conversion efficiency of solar cells.

Due to their remarkable mechanical, thermal and electrical characteristics, silicon carbide (SiC) single-walled nanotubes (SWNTs) are an unusual and promising class of materials. Density functional theory (DFT) is used in this study to examine the electrical and structural characteristics of copper-doped SiC armchair SWNTs. It has been discovered that copper doping of SiC armchair SWNTs alters the materials’ electrical characteristics. SiC SWNTs band gap plays a significant role in influencing the electrical conductivity and optical characteristics of the substance. The energy bands i.e., valence band and conduction band of SiC armchair SWNTs overlapped as copper doping concentration increased, altering the materials’ electrical conductivity and optical characteristics. Additionally, a continuous density of states plot and a narrower band gap are frequently employed as markers of ferroelectric behaviour which indicates the existence of a polarizable and highly delocalized electronic system. The significance of copper doping in SiC SWNTs is understood by this study, along with the effects of the doping on the material’s electrical properties.

A comprehensive investigation was conducted to analyze the physical properties, including electronic structure, optical characteristics, and thermoelectric properties, of four zinc blend structures: BAs, AlAs, BBi, and BSb. This analysis utilized first-principles calculations based on Density Functional Theory (DFT) and Boltzmann transport theories, implemented in the WIEN2K simulator program. The compounds examined displayed intriguing electronic and optical properties, such as low indirect band gaps of 0.726, 1.888, 0.867, and 1.51 eV for AlAs, BAs, BBi, and BSb, respectively. Moreover, these compounds exhibited high absorption in the UV–Visible region. Among the four compounds studied, BAs demonstrated exceptional structural stability due to its high bulk modulus and negative formation energy. The thermoelectric study revealed that the Seebeck coefficient decreased with increasing temperature, while the figure of merit was proportional to temperature enhancement. This behavior suggests that the investigated materials hold promise for applications in visible-light solar cell devices.

The potential applications of the cubic phase of CsNbO₃ perovskite have been explored by examining its elastic, electronic, and photocatalytic characteristics using a first-principles approach. The structural robustness when subjected to pressure has been verified by studying the computed elastic constants. Its substantial elastic moduli, hardness, and toughness values propose its suitability for various engineering applications. A transition from flexibility to fragility is observed at pressures exceeding 10GPa. The CsNbO₃ material demonstrates an indirect and narrow band gap, making it a promising candidate in optoelectronic applications. Changes in the band gap due to pressure indicate adjustments in orbital hybridization. The material’s low effective carrier mass and high carrier mobility anticipate favorable electrical conductivity. Assessments of the potentials at the conduction band (CB) and valence band (VB) edges underscore the remarkable capacity of CsNbO₃ for activities such as water-splitting and promoting sustainable energy production.

The electronic and magnetic properties of Be${}_{1-x}$(Gd,Eu,Tb)${}_x$O (with $x$ values of 0.125, 0.25, and 0.375) were systematically investigated using the full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). Exchange and correlation potentials were computed employing the generalized gradient approximation (GGA) and GGA plus-modified Becke–Johnson potential (TB-mBJ) approximations. Our findings demonstrate that the incorporation of X into BeO induces magnetism in the compound. Specifically, BeO doped with Gd, Eu, and Tb at $x=0.125,0.25$, and 0.375 exhibits half-metallic behavior, characterized by integer magnetic moments. These results indicate the potential of these compounds to serve as novel half-metallic materials for future spintronics applications, offering exciting prospects in the field.

First-principles based calculations were executed to investigate the sensing properties of ammonia gas molecules on a two-dimensional pristine black phosphorene sheet toward its application as a gas sensor and related applications. We discuss in detail the interaction of ammonia gas molecules on the phosphorene single sheet through the structural change analysis, electronic band gap, Bader charge transfer, and density-of-states calculations. Our calculations indicate that phosphorene could be used as a detector of ammonia, where good sensitivity and very short recovery time at room temperature confirm the potential use of phosphorene in detecting ammonia.

BaHfS₃ and BaZrS₃, two chalcogenide perovskites, show significant promise for next-generation optoelectronic devices due to their adjustable bandgaps, excellent carrier mobilities, and versatile properties. Using density functional theory (DFT) via the WIEN2k package, this study reveals their bandgap energies of 2.05eV and 1.63eV, respectively, situating them in the visible range and making them suitable for photovoltaic (PV) applications. Additionally, both materials satisfy thermodynamic criteria for hydrogen production through water splitting, confirming their photocatalytic potential. Their thermoelectric performance, measured by the figure of merit (ZT) also indicates moderate potential at elevated temperatures. Strain engineering further enhances the PV performance, where a biaxial compressive strain of −6% boosts power conversion efficiencies (PCEs) by 8.34% for BaHfS₃ and 3.30% for BaZrS₃. For photocatalysis, uniaxial and biaxial strains optimize optical absorption and water-splitting kinetics. Furthermore, the thermoelectric properties slightly improve under strain effect. These findings highlight the multifunctional potential of BaHfS₃ and BaZrS₃ for PV, photocatalytic, and thermoelectric applications, with strain engineering providing a robust strategy for performance optimization.

Here, we provide the synthesis process as well as theoretical and experimental research on the molecule known as 7-hydroxy-2-(3,4-dihydroxyphenyl)-3-(piperidin-4-yloxy)-4H-chromen-4-one (7THFP). Quantum mechanical calculations (QM) using several functional levels at a standard basis set have been used to calculate all QM calculations and molecular descriptors. Computational techniques were used to obtain the whole range of vibrational frequencies, IR intensity and Raman activity, all showing excellent agreement with the observed results. The molecule’s electron transport characteristics were explained by Mulliken, NBO, mapped isosurface electron density and Highest Occupied Molecular Orbitals (HOMO)-Lowest Unoccupied Molecular Orbitals (LUMO) investigations. The energy difference between the molecular orbitals (MOs) has also been anticipated. The drug candidate’s ADMET and Lipinski’s rule of five models were used to predict its physicochemical and pharmacokinetic properties, including bioactivity score, lipophilicity and toxicity profiles. The physicochemical profiles of 7THFP indicate favorable drug-likeness, bioactivity and reduced toxicity. Subsequently, molecular docking (MD) analyses were conducted to forecast the ligand’s inhibitory impact on the enzymes. The docking score estimation and in vitro analysis of the drug compound validate its anticancer activity. Lastly, the title molecule was evaluated for its proliferation and cytotoxicity effects on human MCF-7 cell lines. These investigations demonstrate that the product exhibits promising characteristics as a drug candidate and may serve as a model for further enhancement.

Novel nonlinear optical (NLO) molecules are designed in order to meet their tremendous demand in the field of optics and electronics. The first attempt of the structural tailoring of disperse orange 3 (DO3)-an azodye is made to develop nineteen derivative molecules (D1-D19). Two approaches were opted for preparing 4 groups of molecules. The first one was the extension of $\pi$-conjugated system and the second strategy was the use of diverse electron donor and acceptor groups to develop unique donor-$\pi$-acceptor systems. Density functional theory (DFT) calculations were performed for in silico characterization of the studied molecules. The polarizability (${\alpha }_o$) and first-order hyperpolarizability (${\beta }_o$) values gave the insight of nonlinear optical response. All the designed molecules with extended conjugation and unique electron donor and acceptor group combination showed remarkably high ${\alpha }_o$ and ${\beta }_o$ values. The highest hyperpolarizability value (42477.48 a.u.) with several thousand increases than ${\beta }_o$ (7113.25 a.u.) of reference DO3, was depicted by D19 of the designed derivatives. This can be attributed to greater intramolecular charge transfer (ICT) in it. Various interaction studies were made and global reactivity descriptors (GRDs) were calculated to determine their chemical nature and stability. The outcome of our study suggests that the designed molecules are potential candidates for NLO applications, like energy conversion for producing tunable lasers and high-resolution spectroscopic studies.

Nitrosourea (NU) and hydroxyurea (HU) are recognized as chemotherapeutic agents. Their efficiency is restricted by the risk of misuse and the release of trace amounts of un-metabolized chemicals into the environment. Numerous potential negative effects may arise from the use of these drugs. Nanomaterials for drug detection are essential in pharmaceutical research, particularly cancer therapeutic applications such as HU and NU. This study sought to investigate the sensitivity of the C${}_{24}$N${}_{24}$ nanocage in detecting HU and NU via density functional theory (DFT). The interactions between HU/NU drugs and the C${}_{24}$N${}_{24}$ nanocage were investigated using optimized geometries, adsorption energies, FMO, NCI, NBO and QTAIM analyses via DFT and TD-DFT at the B3LYP-D3/6-31G(d,p) theoretical level. The adsorption energy estimations of –24.47 kcal/mol for the NUG complex and –19.90 kcal/mol for the HUB complex indicate that the HU/NU medicines are strongly adsorbed onto the C${}_{24}$N${}_{24}$, and the process is exothermic. NCI and QTAIM analyses have shown noncovalent interactions, primarily van der Waals forces, between C${}_{24}$N${}_{24}$ and HU/NU drugs. When HU/NU interacts with the C${}_{24}$N${}_{24}$ surface, new energy levels are generated in the C${}_{24}$N${}_{24}$ PDOS. Upon evaluating the $E_{\text{g}}$ value, sensitivity and recovery time as parameters of the nanocage’s sensing efficacy, it was determined that the HUB complex exhibits the best conductivity (5.67 × 10${}^{12}$ S/m), fine sensitivity (0.2560) and most stability due to its small energy gap of 1.67 eV value. The complex NUG has the lowest recovery time with a value of 5.15 × 10${}^{-17}$ s. As a result of its recovery time, the C${}_{24}$N${}_{24}$ nanocage is highly desirable for its potential application as an HU/NU drug sensor. This demonstrates that HU/NU drugs can be efficiently identified by the C${}_{24}$N${}_{24}$ nanocage. Our findings indicate that the C24N24 nanocage may enhance drug detection (HU/NU), indicating possible pathways for further advancement.

A new approach for the development of nano-sized spectroscopic-based early-warning sensors using molecular electrostatic potentials (MEP) and molecular vibronics (MV) was presented. The use of MEPs allow us to sense and detect specific molecules in elaborated arrays of logical gates which provide the signature of the trapped species and a decision signal of the results of the sensing operation. Molecular vibronics is used to activate/deactivate, control and program the detection process as well as to transmit the information to and from nano-micro interfaces that allow the interaction with microelectronic systems. In order to develop this scenario, it is needed to explain the exact reasons, from an atomistic point of view rather than using phenomenological models the effects of molecules on nanoclusters. We present here a study of silicon-phenyl complexes.

This research is an introduction to density functional theory (DFT), which has been designed for Floating Spherical Gaussian Orbital (FSGO) method for the first time. Our principal objective is to apply a combination of energy functionals to the FSGO densities. The functionals used are separated into exchange and correlation parts. For the exchange part the Becke exchange that includes gradient correction is used. The correlation part has been carried out using Lee, Yang and Parr gradient-corrected functional. Three goals are investigated in this research. Is it possible to apply DFT in the FSGO procedure to obtain the electronic structure of chemical species? Second, is it a stable condition, from the variational point of view, during optimization of exponents and coefficients of each Gaussian? Thirdly, when the two above questions are encouraging, are the results consistent with other results in the literature? In this research we are looking for acceptable answers to the above questions.

In this work we introduce a hybrid ab initio-classical simulation methodology designed to incorporate the chemistry into the description of phenomena that, intrinsically, require very large systems to be properly described. This hybrid approach allows us to conduct large-scale atomistic simulations with a simple classical potential (embedded atom method (EAM), for instance) while simultaneously using a more accurate ab initio approach for critical embedded regions. The coupling is made through shared atomic shells where the two atomistic modeling approaches are relaxed in an iterative, self-consistent manner. The magnitude of the incompatibility forces arising in the shared shell is analyzed, and possible terminations for the embedded region are discussed, as a way to reduce such forces. As a test case, the formation energy of a single vacancy in aluminum at different distances from an edge dislocation is studied. Results obtained using the hybrid approach are compared to those obtained using classical methods alone, and the range of validity for the classical approach is evaluated.

The first-principles calculations based on Density Functional Theory (DFT) within generalized gradient approximation (GGA) of Engel–Vosko–Perdew–Wang and modified exact exchange potential of Becke–Johnson have been introduced for the structural and electronic properties of the Sc_xAl_1-xN alloys, respectively. The present lattice constants calculated for the ScAlN alloys and the end compounds (AlN and ScN) are found to be in very good agreement with the available experimental and theoretical ones. The stable ground state structures of the Sc_xAl_1-xN alloys are determined to be wurtzite for the Sc concentration less than ~0.403 and rock-salt for the higher Sc concentrations. The present electronic band structure calculations within Becke–Johnson scheme are found to be capable of providing energy band gaps of the AlN and ScN compounds very close to the ones of the available experiments and expensive calculations. According to the calculations of Becke–Johnson potential, the Sc_xAl_1-xN alloys in the wurtzite and zinc-blende structures are direct band gap materials for the Sc concentrations in the ranges of (0.056 ≤ x ≤ 0.833) and (0.03125 ≤ x ≤ 0.0625, 0.375 ≤ x ≤ 0.96875), respectively. However, the ScAlN alloys in the rock-salt phase are determined to be direct band gap materials for total range of the Sc concentration considered in this work. While the energy gaps of the RS-AlScN alloys are found to be extending from near ultraviolet to near infrared with a large (negative) bowing, the ones of the WZ-AlScN and ZB-AlScN alloys are determined to be varying in a small energy range around near ultraviolet with a small (negative) bowing.

Structural stability and electronic properties of GaAs${}_{1-x}$P${}_x$ ($0.0\le x\le 1.0$) nanowires (NWs) in zinc-blende (ZB) ($\sim 5\le$ diameter $\le \sim 21$Å) and wurtzite (WZ) ($\sim 5\le \mathrm{\text{diameter}}\le \sim 29$Å) phases are investigated by first-principles calculations based on density functional theory (DFT). GaAs ($x=0.0$) and GaP ($x=1.0$) compound NWs in WZ phase are found energetically more stable than in ZB structural ones. In the case of GaAs${}_{1-x}$P${}_x$ alloy NWs, the energetically favorable phase is found size and composition dependent. All the presented NWs have semiconductor characteristics. The quantum size effect is clearly demonstrated for all GaAs${}_{1-x}$P${}_x$ ($0.0\le x\le 1.0$) NWs. The band gaps of ZB and WZ structural GaAs compound NWs with $\sim 10\le$ diameter $\le \sim 21$Å and $\sim 5\le \mathrm{\text{diameter}}\le \sim 29$Å, respectively are enlarged by the addition of concentrations of phosphorus for obtaining GaAs${}_{1-x}$P${}_x$ NWs proportional to the x values around 0.25, 0.50 and 0.75.

The adsorption behavior and electronic properties of CO and O₂ molecules at the supported Pt and Eu atoms on (5,5) armchair SWCNT have been systematically investigated within density functional theory (DFT). Fundamental aspects such as adsorption energy, natural bond orbital (NBO), charge transfer, frontier orbitals and the projected density of states (PDOS) are elucidated to analyze the adsorption properties of CO and O₂ molecules. The results reveal that B- and N-doping CNTs can enhance the binding strength and catalytic activity of Pt (Eu) anchored on the doped-CNT, where boron-doping is more effective. The electronic structures of supported metal are strongly influenced by the presence of gases. After adsorption of CO and O₂, the changes in binding energy, charge transfer and conductance may lead to the different response in the metal-doped CNT-based sensors. It is expected that these results could provide helpful information for the design and fabrication of the CO and O₂ sensing devices. The high catalytic activity of Pt supported at doped-CNT toward the interaction with CO and O₂ may be attributed to the electronic resonance particularly among Pt-5d, CO-2$\pi$* and O₂-2$\pi$* antibonding orbitals. In contrast to the supported Eu at doped-CNT, the Eu atom becomes more positively charged, which leads to weaken the CO adsorption and promote the O₂ adsorption, consequently enhancing the activity for CO oxidation and alleviating the CO poisoning of the europium catalysts. A notable orbital hybridization and electrostatic interaction between these two species in adsorption process being an evidence of strong interaction. The electronic structure of O₂ adsorbed on Eu-doped CNT resembles that of O${}_2^{-}$, therefore the transferred charge weakens the O–O bonds and facilitates the dissociation process, which is the precondition for the oxygen reduction reaction (ORR).

In this work, a detailed study of the structural, electronic and absorption properties of crystalline 2,6-dimethyl-4-(diphenylmethylene)-2,5-cyclohexadienone with $\alpha$ form ($\alpha$-DDCD) in the pressure range of 0–250GPa is performed by density-functional theory (DFT) calculations. The particular analysis of the variation tendencies of the lattice constants, bond lengths and bond angles under different pressures shows that there occur complex transformations in $\alpha$-DDCD under compression. In addition, it can be see that the $b$-direction is much stiffer than the $a$- and $c$-axes in the structure of $\alpha$-DDCD, suggesting the compressible crystal of $\alpha$-DDCD has anisotropy. Then, by analyzing the bandgap and density of states (DOS) of $\alpha$-DDCD, it is found that the crystal undergoes a phase transformation from semiconductor to metal at 90GPa and it becomes more sensitive under compression. Besides, in the pressure range 110–170GPa, repeated transformations between metal and semiconductor occur four times, suggesting the structural instability of $\alpha$-DDCD in this pressure range. Finally, the relatively high optical activity with the pressure increases of $\alpha$-DDCD is seen from the absorption spectra, and two obvious structural transformations are also observed at 130GPa and 140GPa, respectively.

In this work, we use density functional theory (DFT) calculations to study the structural, electronic and absorption properties of crystalline 2-benzylidene-1-indanone (signed as 2-BI) in the pressure range of 0–300GPa. The detailed analysis of the variation tendencies of the lattice constants, bond lengths and bond angles with increasing pressures shows that there occur several transformations in 2-BI under different pressures. In addition, it can be see that the $a$- and $c$-axis are much stiffer than the $b$-axis in the structure of 2-BI, suggesting the crystal is anisotropic. Then, the analysis of the band gap and DOS (PDOS) of 2-BI indicate that its electronic character has changed at 120GPa into metal phase, but then transfer into excellent insulator at 230GPa. Moreover, the relatively high optical activity with the increasing pressure of 2-BI is seen from the absorption spectra, and three obvious structural transformations are also observed at 60, 120 and 250GPa, respectively.

In this work, a detailed study of the structural, electronic and optical absorption properties of crystalline benzoic acid in the pressure range of 0–300GPa is performed by density functional theory (DFT) calculations. We found that occur complex transformations in benzoic acid under compression occurs, by analyzing the variation tendencies of the lattice constants, bond lengths and bond angles under different pressures. In the pressure range 0–280GPa, repeated formations and disconnections of hydrogen bonds between H1(P1) atom and O1(P1), O2(P4-$x$-$y$-$z$) atoms occur several times, and a new eight-atom ring (benzoic acid dimer) forms at 100GPa and 280GPa. Then, by analyzing the band gap and density of states (DOS) of benzoic acid, it is found that the crystal undergoes a phase transformation from insulator to semiconductor at 240GPa and it even becomes metal phase at 280GPa. In addition, the relatively high optical activity with the pressure increases of benzoic acid is seen from the absorption spectra, and three obvious structural transformations are also observed at 110, 240 and 290GPa, respectively.

In this work, a detailed study of the structural, electronic and absorption properties of crystalline 1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid (nalidixic acid) in the pressure range 0–300GPa is performed by density functional theory (DFT) calculations. The detail analysis of the variation tendencies of the lattice constants, bond lengths and bond angles with increasing pressures shows that complex transformations occur in nalidixic acid under compression. In addition, it can be see that the $a$- and $c$-axes are much stiffer than the $b$-direction in the structure of nalidixic acid, suggesting the crystal is anisotropic. In the pressure range 90–250GPa, repeated formations and disconnections of covalent bonds between C6 (P1 or P4) and O1 (P4 or P1) occur several times, and a new eight-atom ring forms at 90, 160, 190 and 230GPa, respectively. Then, the analysis of the bandgap and density of states (DOS) of nalidixic acid indicates that its electronic character changes at 230GPa into an excellent insulator, but the electron transition is much easier at several pressure regions for the bandgap closing to 0eV. Moreover, as the pressure increases relatively high optical activity of nalidixic acid is seen from the absorption spectra, and two obvious structural transformations are also observed at 200 and 230GPa, respectively.

This is an ab initio study based on the density functional theory that uses GGA-PBE as the exchange–correlation potential. The energetic, electronic, magnetic properties, and optical conductivity of the cubic $\beta 2$ of TiCo and TiNi alloys with and without the hydrogen atom are performed. The present alloys are found to be thermodynamically stable and can be created. It can be deduced that the octahedral site has higher energetic stability absorption for the hydrogen atoms compared to the bridge and tetrahedral sites in the TiCo and TiNi alloys. The absorption energy at octahedral site is found to be 2.37eV for TiCo and 2.32eV for TiNi. Hydrogen absorption expands and brittles the host alloy. Hydrogen storage in more than one site in the host alloy is found to be energetically stable and can be formed. The chemical bonding between the constituent atoms of the present alloys is mainly ionic with some covalent bonding. The hydrogen absorption has a clear effect on the magnetic, and electrical conductivity relative to the relaxation time and optical conductivity of the present alloys. Beneficial optical applications can be assumed for the present alloys due to their high optical conductivity.

In this paper, the structural, electronic and absorption properties of 2,2′-iminobis (acetamide oxime) (IBO) under pressure of 0–300GPa are calculated by the density functional theory (DFT) calculations. Analysis of the variation trend of lattice constant, bond length and bond angle of IBO under compression conditions, shows there are complex transformations under different pressure. In addition, it is found that the structure of IBO in the $a$-axis is stiffer than that along the $b$- and $c$-axes, which indicates that the crystal has anisotropic compressibility. By analyzing the band structure and the density of states of IBO, it is seen that at 120GPa, the electronic structure of IBO changes into metallic system, and becomes more sensitive under compression conditions. The transition between metal and semiconductor occurs again at 150Gpa. Finally, at 180GPa, the crystal transforms into metal again. The three obvious phase transitions indicate that the structure of IBO becomes more unstable with the increase of pressure. The absorption spectra show that with the increase of pressure, the optical activity of IBO crystal grows higher, and three obvious structural transitions are, respectively, observed at 120, 150 and 180GPa.

In this work, the structural, electronic and absorption properties of 2-methyl-2H-naphtho-[1,8-de]triazine in the pressure ranges of 0–250GPa are studied in detail (hereinafter referred to as 2-methyl crystal). Density functional theory (DFT) is used to calculate the lattice constants, bond lengths and bond angles of 2-methyl under different pressures. The results show that the crystals undergo complex transformations under compression, and the major structural transformations occur at pressures of 90GPa and 210GPa with repeated formations and disconnections. In addition, the $a$- and $c$-directions of the 2-methyl are stiffer than the $b$-direction, which indicates that the compressibility of the crystal is anisotropic. From the specific analysis of the bandgaps of 2-methyl, we can know that the crystal is converted from semiconductor to metal at 90GPa. The absorption spectrum of the crystal also indicates that 2-methyl has a relatively high optical activity with the increasing pressure.

In this work, detailed DFT calculations of the structural, mechanical and electronic properties of crystalline CaSi₂ with four different structures in the pressure range of 0–50 GPa are performed by GGA-PBE. It is found that the Enthalpy differences imply that the R$\bar{3}$m phase $\to$ I4₁/amd phase $\to$ P6/mmm phase transition in CaSi₂ occur at $P_1=2.5$GPa, $P_2=33.5$GPa by using the XC of GGA, which is consistent with previous experiments and theoretical conclusions. Besides, the elastic stability criterion is used to study the change of the elastic constant of CaSi₂ under pressures. In particular, the bulk modulus $B$, shear modulus $G$, Young’s modulus $E$, sound velocity $v$ and brittleness and toughness properties of CaSi₂ under pressures are comprehensively studied for the first time. Finally, the changes of the anisotropy factor of CaSi₂ are studied under different pressures, and the electronic structure is studied in detail.

In this paper, the structural, electronic and optical absorption properties of $m$-aminobenzoic acid crystals (hereinafter referred to as $m$-amino) in the pressure range of 0–300GPa are calculated by density functional theory (DFT). The changing trend of the lattice constant of $m$-amino under different pressures is analyzed. We find that the crystal undergoes complex transformation. Furthermore, it can be seen that the structure of $m$-amino along the $b$-axis is stiffer than that along the $a$-axis and $c$-axis, suggesting that the crystal has anisotropic compressibility. Through the analysis of the band gap and density of states of $m$-amino, it is found that the electronic properties of $m$-amino are transformed from semiconductor phase to metal phase at 100GPa, then jump into the semiconductor phase and maintain the metal phase again in the pressure range of 150–250GPa. Repeated phase transitions indicate that the structure of $m$-amino becomes more unstable as the pressure increases. Besides, from the absorption spectra, the optical activity of $m$-amino is relatively high with the increase of pressure, and two obvious structural transitions are observed at 70 and 270GPa, respectively.

We investigate the electronic structure and the optical characterizations of iron incorporating titanium dioxide by ab initio method by employing the density functional theory. We show that Fe atoms can be incorporated into TiO₂ by replacing Ti atoms in the crystal structure of ${\mathrm{\text{Fe}}}_x{\mathrm{\text{Ti}}}_{1-x}{\mathrm{\text{O}}}_2$ according to the ratio $X=0.00$, 0.25, 0.50, 0.75 and 1.00. The partial density of state and the energy band structure of the optimized structure have been calculated. Adding Fe atoms to the TiO₂ causes shrinkage of the bands in the band structure that leads to a decrease in the energy gap of the pure titanium dioxide crystal structure. The results of the optical properties showed that the titanium dioxide has no absorption in the range of the visible light and detect only in the ultraviolet light (UV). The optical constant absorption coefficient, reflectivity and real and imaginary parts of the dielectric constant have been calculated. It exhibits that the properties of pure TiO₂ will change by adding the Fe atoms to the structure, which leads to a significant enhancement in the optical characteristics.

In this work, a detailed study of the structural, mechanical and thermodynamic changes in CaZn₂ under pressure range of 0–40 GPa is performed, and two different exchange correlations (XC) of GGA-PBE and LDA are used. It is found that the enthalpy values imply that CaZn₂ undergoes a phase transition from CeCu₂-type phase to Laves phase at 3.45 GPa with XC of GGA-PBE and 1.43 GPa with LDA, which is consistent with previous experiments and parts of theoretical conclusions. Furthermore, the elastic stability criterion is used to study the elastic constants of CaZn₂ under different pressures, confirming the stability of the CaZn₂ structure from 0 GPa to 40 GPa. Finally, the thermodynamic properties of CaZn₂ under pressures are comprehensively studied in detail.

In this paper, density functional theory (DFT) is used to study the structure, electron and absorption properties of 6-Amino crystal in the pressure range of 0–300GPa. The variations of the lattice constants, bond lengths and bond angles show that they undergo complex transformations under different pressures. More narrowly, the covalent bonds of the benzene ring and the uracil ring in the planar intramolecular structure are broken, and then the new covalent bonds between the adjacent intermolecular structure are reshaped at about 80, 100 and 160GPa. The analysis results of band gap and DOS of 6-Amino indicate that the electronic properties of 6-Amino repeatedly transform from the semiconductor system into the metal phase at 80, 180 and 260GPa. The absorption spectra show two important structural changes at 100 and 180GPa, and present the high optical activity with the change of pressure.

Solid-state thermoelectric devices offer the possibility of exploiting waste heat from engines and power plants and converting it into electrical energy. One of the greatest challenges in the development of thermoelectric material systems is to find new thermoelectric materials with high thermoelectric figures of merit ZT. In this work, the structural, electronic and thermoelectric properties of PbSe${}_{1-x}$S${}_x$ ($x=0$, 0.25, 0.50, 0.75 and 1) semiconductors are investigated by applying density functional theory in a full potential linearized augmented plane wave method (FP-LAPW). Calculations of structural properties were completed using the generalized gradient approximation GGA of Perdew Burke and Ernzerhof PBE to get reliable lattice constant results with experimental values. The obtained electronic results show that the PbSe${}_{1-x}$S${}_x$ material is a narrow band gap semiconductor. In addition, the thermoelectric properties are studied on the basis of the fully iterative solution of the Boltzmann transport equation. PbSe${}_{1-x}$S${}_x$ had a high figure of merit indicating that our materials are promising candidates in thermoelectric applications.

The electronic band structure of AlN, AlSb, AlAs and their ternary alloys with In has been investigated by ETB. The ETB method has been formulated for sp³d² basis and nearest neighbor interactions of the compounds and its energy parameters have been derived from the results of the present first principles calculations carried on AlN, AlSb and AlAs. It has been found that the present ETB energy parameters can produce the band structure of the compounds and their ternary alloys with In successfully.

The electronic band structure of GaN and GaAs has been investigated by ETB to obtain the band gap bowing of In_xGa_1-xAs_1-yN_y alloys lattice matched to GaAs. The ETB method has been formulated for sp³d² basis and nearest neighbor interactions of the compounds, and its energy parameters have been derived from the results of the present first principles calculations carried out on GaN and GaAs. It has been found that the present ETB energy parameters are capable of producing the electronic band structure of corresponding compounds and the large bowing parameter of InGaAsN alloy.

We investigated the electron transport properties of thiophen-bithiol-based molecular wires through atomic metal–thiophen–metal systems using the first principle methods. Various metal–thiophen–metal atomic systems are constructed with different end atoms (S, Se, and Te). The electron transport of the atomic system is systematically studied by analysis of transmission function, density of states, and current–voltage characteristics of the systems.

First principles total energy calculations within the density functional formalism have been used to investigate the electronic, mechanical, and optical properties of pseudocubic-Si₃P₄ and Ge₃P₄. Considering the technological importance of the Si/Ge-Group-V elements, we have concentrated mainly on the comparatively less studied, but energetically more favorable pseudocubic-Si₃P₄ and Ge₃P₄ structures of the Si and Ge phosphides. We find that the electronic band structures show that pseudocubic-Si₃P₄ and Ge₃P₄ are both indirect band semiconductors with very low density functional band gaps of 0.24 eV and 0.13 eV, respectively. We also calculate mechanical properties of the materials, such as the bulk modulus, elastic constants, shear modulus, and Vickers hardness of the two phosphides. We find that the bulk and shear modulus of pseudocubic-Si₃P₄ and Ge₃ P₄ are 76.18 GPa and 58.37 GPa, and 59.99 GPa and 46.92 GPa, respectively. Pseudocubic-Si₃P₄ and Ge₃ P₄ have low Vickers hardness, nearly 18.88 and 16.86 GPa, respectively. Moreover, optical parameters, including dielectric function, refractive index, optical absorption, energy loss function, and plasma frequency are also studied.

A survey of recent studies of biaxial liquid crystals (LCs), whose nematic and/or smectic-A phases do not possess optical uniaxiality (viz., more than one optical axis exists), is given in this review. In particular, we emphasize on how Nuclear Magnetic Resonance (NMR) spectroscopy can help to advance the understanding of phase biaxiality in general, and to examine recent debates on the existence of biaxial nematic phase reported in low molecular mass bent-core or V-shaped mesogens. A general discussion of orientational order parameters is detailed, particularly in smectic-C (SmC) and biaxial nematic phases. How these orientational order parameters can be determined by various techniques such as NMR, IR absorbance and Raman scattering studies, will be mentioned. Recent X-ray observations of SmC clusters in the nematic phase of V-shaped mesogens are highlighted and contrasted with probable theory. Moreover, deuterium and carbon-13 NMR techniques are briefly reviewed, and their possible utilization to identify phase biaxiality in these biaxial LC systems is explored.

We adapt the classical Ornstein-Zernike equation for the direct correlation function of classical theory of liquids in order to obtain a model for the exchange-correlation hole based on the electronic direct correlation function. Because we explicitly account for the identical-particle nature of electrons, our result recovers the normalization of the exchange-correlation hole. In addition, the modified direct correlation function is shorted-ranged compared to the classical formula. Functionals based on hole models require six-dimensional integration of a singular integrand to evaluate the exchange-correlation energy, and we present several strategies for efficiently evaluating the exchange-correlation integral in a numerically stable way.

The study of bimetallic catalysts has scientific and technologic importance because of special catalytic activity towards several reactions. RhCu is an interesting bimetallic system due to combination of the very different catalytic activities of Rh and Cu. The catalytic activity of this bimetallic does not result from simple interpolation of the constituents. In fact, at low Cu content, the catalytic activity of RhCu is superior to that of Rh but when the Cu content is higher the activity decays. This is a curious trend which theoretical works had attempted to explain. This paper reports an overview of the most recent research works about this bimetallic system with emphasis in its especial characteristics.

The quest for novel low-dimensional materials has led to the discovery of graphene and thereafter, a tremendous attention has been paved in designing of its fascinating properties aiming in fabricating electronic devices. Using first-principles calculations, we study the structure, energetic and electronic as well as magnetic properties of graphene induced by the interactions in presence of both external and internal foreign agents in detail. We find that a variety of tunable electronic states, e.g., semiconductor-to-half-metal-to-metal and magnetic behaviors can be achieved under such hierarchical interactions and their influence. We also find that the nature and compositions of foreign substances play a key role in governing the electro-magnetic characteristics of these nanomaterials. In this review, we suggest a few routes for engineering the tunable graphene properties suitable for future electronic device applications.

Electronic band structure and optical parameters of ZnAl₂O₄ are investigated by first-principles technique based on a new potential approximation, known as modified Becke–Johnson (mBJ). This method describes the excited states of insulators and semiconductors more accurately The recent direct band gap result by EV-GGA is underestimated by about 15% compared to our band gap value using mBJ-GGA. The value of the band gap of ZnAl₂O₄ decreases as follows: E_g(mBJ-GGA/LDA) > E_g(GGA) > E_g(LDA). The band structure base optical parametric quantities (dielectric constant, index of refraction, reflectivity and optical conductivity) are also calculated, and their variations with energy range are discussed. The first critical point (optical absorption's edge) in ZnAl₂O₄ occurs at about 5.26 eV in case of mBJ. This study about the optoelectronic properties indicates that ZnAl₂O₄ can be used in optical devices.

Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF₃ (A = Cs; M = Ca and Sr) compounds. The calculations are based on the total-energy calculations within the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated by local density approximation (LDA) and generalized gradient approximation (GGA). The structural properties, including lattice constants, bulk modulus and their pressure derivatives are in very good agreement with the available experimental and theoretical data. The calculations of the electronic band structure, density of states and charge density reveal that compounds are both ionic insulators. The optical properties (namely: the real and the imaginary parts of the dielectric function ε(ω), the refractive index n(ω) and the extinction coefficient k(ω)) were calculated for radiation up to 40.0 eV.

In the present study, ground state and elastic properties of semiconductor MgSe in zinc-blende phase are investigated using density functional theory (DFT). Exchange-correlation potentials are approximated with the generalized gradient approximation (GGA). From the calculated bulk modulus, we determine the refractive index, plasmon energy, cohesive energy and micro-hardness of the MgSe semiconductor binary alloy. The density of state (DOS), projected density of state (PDOS), phonon dispersion frequencies, charged density, electronic band structure and dielectric functions are also reported. From the band structure, a direct band gap of 2.50 eV was observed in close agreement with other reported calculations, but lower than the experimental value of 3.60 eV. Along the high symmetries directions, we found a striking resemblance between MgSe and a III–V semiconductor, while the high cohesive energy in MgSe suggests filled bonding orbitals which might result in decrease in atomic volume with corresponding increased compression of the s-orbitals under any transition series.

Bonding nature as well as structural, optoelectronic and thermal properties of the cubic XMg₂O₄(X = Si, Ge) spinel compounds have been calculated using a full-potential augmented plane-wave plus local orbitals (FP-APW+lo) method within the density functional theory. The exchange-correlation potential was treated with the PBE-GGA approximation to calculate the total energy. Moreover, the modified Becke–Johnson potential (TB-mBJ) was also applied to improve the electronic band structure calculations. The computed ground-state parameters (a, B, B′ and u) are in excellent agreements with the available theoretical data. Calculations of the electronic band structure and bonding properties show that these compounds have a direct energy band gap (Γ-Γ) with a dominated ionic character and the TB-mBJ approximation yields larger fundamental band gaps compared to those obtained using the PBE-GGA. Optical properties such as the complex dielectric function ε(ω), reflectivity R(ω) and energy loss function L(ω), for incident photon energy up to 40 eV, have been predicted. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the effects of pressure P and temperature T on the thermal expansion coefficient, Debye temperature and heat capacity for the considered compounds are investigated for the first time.

We present the results of a density functional theory study of high-pressure structures of HgTe up to bcc structure, which is the highest-pressure structure that has been fully characterized in experiments in the compounds. We investigated the different structures of HgTe and studied the semimetal → semiconductor → conductor transition in detail. We found, in the mechanism for the semimetal → semiconductor transition, the local structure plays a very important role. Change in local structure leads to the change in hybridization of bonding, sp³ →sp³d² and led to the change from semiconductor to conductor. In addition, we focused on the special transition of semimetal → semiconductor. The tiny change of bond angle reduces the p–d repulsion interaction in the compound and a band gap is open up, which indicates the semiconductor property.

Density functional theory and generalized gradient approximation have been employed to study Mg, Si and O vacancies in the Mg₂SiO₄ forsterite mineral. Microstructure of defect equilibrium geometries, electronic properties as well as chemical bonding in the region surrounding each one of the vacancies have been computed and discussed in detail. It is found that vacancies tend to increase covalent character of the chemical bonding for atoms situated in their vicinity independently of the type of vacancy. Nevertheless, obtained atomic distortion in the region surrounding vacancies generally obeys Coulomb electrostatic interaction law. Local energy states are found in the band-gap region due to the occurrence of vacancy-type defects. These findings are discussed in light of the available experimental data.

The phonon spectra, band structure and density of states of cubic perovskite SnTiO₃ were investigated using first-principles density functional theory (DFT) computation. The potential energy curves of cations displacement and the formation energy of Sn substitution to B-site were calculated to estimate the structure stability. The results indicate that perovskite SnTiO₃ is a promising ferroelectric end member for lead-free piezoelectric materials and applications.

Structural, elastic, electronic and optical properties as well as chemical bonding of the binary alkali metal selenides M₂ Se (M = Li, Na, K, Rb) were calculated using the full potential linearized augmented plane method. From the elastic constants it is inferred that these compounds are brittle in nature. The results of the electronic band structure show that Na₂Se has a direct energy band gap (Γ-Γ), Li₂Se has an indirect energy band gap (Γ- X), while K₂Se and Rb₂Se have an indirect energy band gap (X-Γ). Analysis of the charge distribution plots reveals a dominated ionic bonding in the herein studied compounds. Additionally, we have calculated the optical properties, namely, the real and the imaginary parts of the dielectric function, refractive index, extinction coefficient, optical conductivity and reflectivity for radiation up to 30.0 eV. All these compounds have direct energy band gap greater than 3.1 eV suggesting their use for manufacturing high frequency devices.

The structural, electronic thermodynamic and thermal properties of Ba_xSr_1-xTe ternary mixed crystals have been studied using the ab initio full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). In this approach, the Perdew–Burke–Ernzerhof-generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. Moreover, the recently proposed modified Becke Johnson (mBJ) potential approximation, which successfully corrects the band-gap problem was also used for band structure calculations. The ground-state properties are determined for the cubic bulk materials BaTe, SrTe and their mixed crystals at various concentrations (x = 0.25, 0.5 and 0.75). The effect of composition on lattice constant, bulk modulus and band gap was analyzed. Deviation of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence (LCD) were observed for the ternary Ba_xSr_1-xTe alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ΔH_m as well as the phase diagram. It was shown that these alloys are stable at high temperature. Thermal effects on some macroscopic properties of Ba_xSr_1-xTe alloys were investigated using the quasi-harmonic Debye model, in which the phononic effects are considered.

Structural and electronic properties of perovskite KCaX₃ (X = F and Cl) compounds are investigated using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k code. The exchange-correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Based on these calculations, it has been concluded that KCaX₃ compounds have indirect energy band-gap (Γ-R). Moreover, the theoretical investigation which has been carried out on the highly hydrostatic pressure dependence of the KCaX₃ electronic properties revealed a linear relationship between both the hydrostatic pressure and the energy band-gap. In addition, the electronic and bonding properties of the band structure, density of states (DOS) and electron charge density have been calculated and presented. Besides that, the dielectric function, refractive index and extinction coefficient are calculated. The origin of some of the peaks in the optical spectra is discussed in terms of the calculated electronic structure. Finally, the calculated structural properties are found to agree well with the available experimental and theoretical data.

Encapsulation of small clusters in fullerene cages provides a stable environment for their application in nanoscale functional devices. In this paper, first principles study of Ruthenium as an endohedral dopant in buckminsterfullerene has been carried out using density functional theory. Ruthenium atom has three stable dopant sites inside C₆₀, with three possible values of magnetic moment (4, 2 and 0 μB). The doping position of Ru atom can be seen to have an effect on HOMO–LUMO gap, formation energy, binding energy and magnetic moment of the fullerene cage. The interaction between Ru and C atoms in different conformations can be explained in terms of Mulliken analysis and density of states analysis. It is also possible to encapsulate more than one Ru atoms in the C₆₀ cage (Ru_n@C₆₀, n = 2–6); encapsulation up to six atoms has been analyzed, after which the process is energetically unfavorable. The geometry of the lowest energy structures, compared to the isolated Ru_n clusters, is found to change as a result of encapsulation (e.g., in Ru₃@C₆₀ and Ru₅@C₆₀). A reduction in magnetic moment of Ru clusters inside fullerene cage as compared to isolated clusters also occurs due to hybridization and confinement effects. The varied magnetic moments of Ru-encapsulated C₆₀ molecules reveal its applications in molecular magnetic devices and quantum peapods.

Optical properties of Zn_1-xMg_xS, Zn_1-xMg_xSe and Zn_1-xMg_x Te(0 ≤ x ≤ 1) ternary semiconductor alloys are calculated using the full potential linearized augmented plane wave within the density functional theory. The exchange correlation potential is treated by the generalized gradient approximation (GGA) within Perdew et al. scheme. The real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the extinction coefficient k(ω), the optical absorption coefficient α(ω), the reflectivity R(ω) and the electron energy loss function (EELS) are calculated within random phase approximation (RPA). Our results are compared with the previous theoretical calculations and available experimental data. Moreover, the interband transitions responsible for the structures seen in the spectra are specified. It is shown that, the chalcogen p states as initial and Zn4s, Mg3s, chalcogen d states as final states perform the major role in optical transitions.

The phase stability and electronic properties in Al₃Ta compound are studied using the FP-LAPW method. In this approach, the generalized gradient approximation (GGA) is used for the exchange-correlation potential calculation. The total energy calculations show that the D0₂₂ structure is more stable than that of D0₂₃ and L1₂. The densities of states exhibit a pseudo gap near the Fermi level for all considered structures. By analyzing the electronic charge density we find a build-up of electrons in the interstitial region, and the bonds are directed from the Ta atoms to the Al atoms, which is the characteristic of covalent bonding. The temperature and pressure effects on the structural parameters, Debye temperature, Grüneisen parameter, heat capacities (C_v, C_p) and thermal expansion are predicted through the quasi-harmonic Debye model.

We have investigated theoretical Vickers hardness, thermodynamic and optical properties of four zirconium metal-based MAX phases Zr₂AC (A = Al, Si, P and S) for the first time in addition to revisiting the structural, elastic and electronic properties. First-principles calculations are employed based on density functional theory (DFT) by means of the plane-wave pseudopotential method. The theoretical Vickers hardness has been estimated via the calculation of Mulliken bond populations and electronic density of states. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats and volume thermal expansion coefficient of all the compounds are derived from the quasi-harmonic Debye model. Further, the optical properties, e.g., dielectric functions, indices of refraction, absorption, energy loss function, reflectivity and optical conductivity of the nanolaminates have been calculated. The results are compared with available experiments and their various implications are discussed in detail. We have also shed light on the effect of different properties of Zr₂AC as the A-group atom moves from Al to S across the periodic table.

We carried out ab initio calculations of structural, electronic and optical properties of Indium nitride (InN) compound in both zinc blende and wurtzite phases, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). For the exchange and correlation potential, local density approximation (LDA) and generalized gradient approximation (GGA) were used. Moreover, the alternative form of GGA proposed by Engel and Vosko (EV-GGA) and modified Becke–Johnson schemes (mBJ) were also applied for band structure calculations. Ground state properties such as lattice parameter, bulk modulus and its pressure derivative are calculated. Results obtained for band structure of these compounds have been compared with experimental results as well as other first principle computations. Our results show good agreement with the available data. The calculated band structure shows a direct band gap Γ → Γ. In the optical properties section, several optical quantities are investigated; in particular we have deduced the interband transitions from the imaginary part of the dielectric function.

This study combines the use of the full potential linear-augmented plane wave method (FP-LAPW) within the framework of the density functional theory (DFT) and the optical matrix approach for modeling the multilayer assembly. A new class of heterostructures with sufficient number of alternating layers of rutile-TiO₂ (as a high index material) and α-Al₂O₃ (as a low index material) are proposed and their transmittance spectra are investigated. This study shows that the number of alternating layers, and the thickness and arrangement of them should be considered in making a heterostructured filter. The relation between heterostructure parameters and narrow-band-pass peaks of transmittance spectra is investigated. The proposed model seems to be successful in predicting the optical behavior of heterostructures and simulations agree well with the experimental observations. In addition, our model is very flexible and the effect of other parameters such as incident angle and light polarization can be easily investigated.

The theoretical calculations indicate that the metal-doped boron nitride (BN) sheets are potential materials to store the hydrogen and tune the bandgap. It is all known that the BN sheet is a nonmagnetic wide-bandgap semiconductor. Using density function theory (DFT), the lattice parameters of Cr-doped BN sheets are optimized, which are still kept on two-dimensional (2D) planar geometry, and the bandgap and ${\mathrm{\text{H}}}_2$ storage are studied. The simulation results show that the ${\mathrm{\text{H}}}_2$ molecule can be easily absorbed by Cr-doped N in BN sheet. As the adsorption energy was greatly decreasing with the increasing number of Cr-doped N, B had an affinity for adsorption of ${\mathrm{\text{H}}}_2$. With the increase of Cr doping, the bandgap of Cr-doped BN sheet is decreasing. The bandgap decreases from 4.705 eV to 0.08 eV. So Cr-doped BN sheet is a promising material in storing ${\mathrm{\text{H}}}_2$ and tuning the bandgap.

Structures and stabilities of ${({\mathrm{\text{Os}}}_n\mathrm{\text{N}})}^{0,\pm }$ clusters have been systematically studied via using density functional theory (DFT) with generalized gradient approximation (GGA). The calculations show that the stable configurations of ${({\mathrm{\text{Os}}}_n\mathrm{\text{N}})}^{0,\pm }$ are such structures with one N atom bonded to the external of the basic constructions consisting of Os atoms. Meanwhile, ${({\mathrm{\text{Os}}}_n\mathrm{\text{N}})}^{0,\pm }$ clusters $(n=7-9)$ represent “magic number” effect, and 8 is the magic number. Additionally, the ground-state structures of ${({\mathrm{\text{Os}}}_8\mathrm{\text{N}})}^{0,\pm }$ clusters have the best stability, while that of ${\mathrm{\text{Os}}}_7\mathrm{\text{N}}$ cluster possesses the worst stability. The result of the study on the ionization potential (IP) and the electron affinity (EA) shows that there are not topological differences among the configurations of ${({\mathrm{\text{Os}}}_n\mathrm{\text{N}})}^{0,\pm }$$(n=7-11)$ clusters.

In this study, we investigated stable structures for a transition metal atom–boron (CrB) wheel-like clusters and compared them with their corresponding 3D counterparts by means of density functional theory (DFT). In addition, hydrogen storage capability of the wheel-like system was investigated. All simulations were performed at the B3LYP/TZVP level of theory. We set out a complete route to the formation of CrB wheel-like clusters. Our results showed that, some of the clusters, investigated in this work (CrB_n; n = 4, 6, 7, 8), either prefer to be in a 3D geometry rather than 2D quasi-planar or planar geometry. However, hydrogen doping has an interesting effect on both 2D quasi-planar and 3D geometries of this system. Simply it transforms the 3D structure, first, into a 2D quasi-planar, then a planar geometry. Furthermore, our results show that H–cluster interaction is too high for reversible hydrogen storage for these clusters.

The electronic structure, mechanical and thermodynamic properties of Fe₂VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe₂VAl and Fe₂VGa are predicted with pressure and temperature in the ranges of 0–40 GPa and 0–1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

Energetically stable Ge diamondoids are used as building blocks to investigate Ge nanocrystal properties using density functional theory (DFT). Energy gap, HOMO and LUMO of Ge diamondoids vary according to confinement theory with shape fluctuations. Ge diamondoid vibrational force constants reach 2.18 mDyne/Å which is between that of bulk silicon and tin. Ge–Ge vibrational frequencies and reduced masses reach 357.47 cm${}^{-1}$ and 41.93 amu, respectively, which are higher than the values of bulk Ge. Size variation of UV–Vis shows that the maximum optical peak moves from 163 nm to nearly 290 nm as the size of Ge diamondoids and molecules increases. The higher peak value approaches that of experimental Ge quantum dots at 300 nm. NMR spectra of Ge diamondoids are analyzed as a function of diamondoid sizes. Our results show that all investigated spectroscopic tools are sensitive to molecular or nanocrystals size. NMR is particularly good size indicator. Natural bond orbital (NBO) population analysis shows present diamondoid bondings differ from ideal $s{p}^3$ bonding. The bonding for Ge valence orbitals is in the range $(4s^{1.24}4p^{2.60})-(4s^{1.27}4p^{2.73})$ depending on distance between Ge atom and diamondoid surface. Highest Ge diamondoids vibrational longitudinal optical (LO) mode is blue shifted with respect to experimental bulk value which is the opposite case for C and Si. H surface atom effects on electronic and vibrational properties are discussed.

The electronic, thermoelectric, optical, and magnetic properties of the samarium aluminate (SmAlO₃) compound is studied using the spin-polarized full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). The exchange and correlation potential is treated with the generalized gradient approximation (GGA) and the Coulomb repulsion ($U=0.51$ Ry) has been calculated theoretically and was used for the GGA$+U$ based approximated electronic structures. Additionally, the modified Becke–Johnson (mBJ) potential was also utilized along with the GGA$+U$ approach for the calculation of the band gap. On the other hand, the optical properties were analyzed with the mBJ$+U$ results and the thermoelectric properties were explained on the basis of the electronic structures and density of states (DOS) with a thermoelectric efficiency of 0.66 at 300 K. The minimum reflectivity at 1.13 eV (which was equal to 1.097 $\mu$m) was found to be in agreement with the experimental results. Further refinements in the electronic structures were obtained by adding the spin–orbit coupling (SOC) interactions to the GGA$+U$ approach, which was then combined with the mBJ approximations. Hence, a conclusion using the combined mBJ$+U+$SOC study indicates that the SmAlO₃ compound is a potential candidate for both thermoelectric as well as magnetic devices.

This paper communicates the structural, electronic and optical properties of L-alanine, monofluoro and difluoro substituted alanines using density functional calculations. These compounds exist in orthorhombic crystal structure and the calculated structural parameters such as lattice constants, bond angles and bond lengths are in agreement with the experimental results. L-alanine is an indirect band gap insulator, while its fluorine substituted compounds (monofluoroalanine and difluoroalanine) are direct band gap insulators. The substitution causes reduction in the band gap and hence these optically tailored direct wide band gap materials have enhanced optical properties in the ultraviolet (UV) region of electromagnetic spectrum. Therefore, optical properties like dielectric function, refractive index, reflectivity and energy loss function are also investigated. These compounds have almost isotropic nature in the lower frequency range while at higher energies, they have a significant anisotropic nature.

In previous researches it is demonstrated that reactivity and sensitivity of boron nitride nanotubes (BNNTs) toward gas molecules can be modified by impurity. In this work, oxygen defect for three nitrogen sites was used to study the adsorption of NO molecule through the surface of boroxol ring of oxygen doped BNNT (7,0) with different adsorption patterns, including side-on and end-on. All calculations are performed using the DFT-B3LYP/6-31G${}^{\ast }$ level of theory, and their electronic energies are corrected by gCP and D3 correction terms. High binding energies indicate that NO molecule undergoes chemical adsorption with large charge transfer from the tube which can significantly change electronic properties of the tube. Density of state (DOS) and partial DOS (PDOS) analyses revealed that adsorption of NO molecule on the boroxol ring position is covalent in nature with significant effect on the electronic properties of tube. The Laplacian of electron density, Lagrangian kinetic energy density, Hamiltonian kinetic energy density and potential energy density at bond critical points between the tube and NO indicate that the interaction between the tube and NO molecule is covalent in nature. Topological analysis of the electron localization function shows that electrons in the new formed bonds are approximately localized, meaning that the nature of adsorption process is chemical covalent. The studied nanotube is a suitable candidate to filter and eliminate NO gas molecule.

The ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnS}}}_4$, ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnSe}}}_4$ and ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnTe}}}_4$ and their alloys have been frequently investigated experimentally owing to their suitable bandgap for the solar cell applications. For the first time, density functional theory is applied to explore the structural, electronic and optical properties of ${\mathrm{\text{Cu}}}_2\mathrm{\text{ZnSn}}({\mathrm{\text{S}}}_{1-x}{\mathrm{\text{Te}}}_x)$ and ${\mathrm{\text{Cu}}}_2\mathrm{\text{ZnSn}}({\mathrm{\text{Se}}}_{1-x}{\mathrm{\text{Te}}}_x)$$(x=0,0.25,0.5,0.75,1)$. The energy minimization procedure reveals that the Kesterite phase is stable compared to the Stannite structure. Lattice constants of the compounds are in good agreement with the previous experimental results. The alloys have direct bandgaps which decrease by increasing the concentration of Te. The chemical bonding among the cations and anion is dominantly covalent. Electronic bandgap dependent optical properties like absorption coefficient and optical conductivity are studied in detail. The materials show strong response in the visible region of energy spectrum indicating the usefulness of these materials for optoelectronic devices.

We report the structural, electronic, optical, and thermoelectric properties of the five cubic alkali-earth transition-metals AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) using density functional theory. Structural properties, electronic structures and optical behaviors are calculated explicitly via highly accurate contemporary full potential-linearized augmented plane wave (FP-LAPW) method. The investigated ground state data of these materials is quite close to the experimental information. The modified Becke–Johnson (mBJ) predicts the intermetallic nature of AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) materials. The complex dielectric function of these intermetallic compounds has been calculated and the observed noticeable peaks are examined through mBJ. With the help of complex dielectric function, the other important optical parameters like reflectivities, conductivities and refractive indices of AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) have been calculated as a function of energy. The optical response suggests that AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) compounds can be used for the optoelectronic devices. Further, the thermoelectric properties have been calculated through BoltzTraP program, the calculated values for different thermoelectric parameters recommend that these AZn${}_{13}$ (A-Na, K, Ca, Sr, Ba) materials are the suitable candidates for thermoelectric applications.

Mechanical and electronic properties of oxygen plasma-treated graphene sheets are investigated using density functional theory (DFT). Oxygen plasma-treated graphene is modeled using a graphene sheet with adsorbed epoxide functional groups (C–O–C) on its one side. The most stable configurations of such oxidized graphene sheets with different O/C ratios ranging from 12.5% to 50% are then calculated. In the special case of O/C = 50% (fully oxidized surface), both single- and double-sided oxidation cases are considered. The elastic and electronic properties of the energetically most favorable configurations are evaluated under the tensile and compressive loads in harmonic range. For structures with high O/C ratios (O/C $\ge$ 25%), the elastic constants (modulus of elasticity and bulk modulus) are significantly smaller than those of graphene while for low O/C ratios (O/C $\le$ 12.5%), these quantities are almost equal to the elastic constants of pristine graphene. We also found that the electronic bandgap of the oxidized sheets is increased under tensile loading.

First-principles study of elastic, electronic and optical properties of full-Heusler Co₂V(Al, Ge, Ga and Si) compounds are calculated through density functional theory (DFT) to obtain and compare the mentioned properties. Equilibrium lattice constants of these compounds are in good agreement with other works. Electronic calculations are shown full spin polarization at Fermi level for all compounds, so in the down spin, indirect bandgap is calculated as 0.33, 0.6, 0.2 and 0.8 eV for Co₂V(Al, Ge, Ga and Si), respectively. The integer amounts of the magnetic moments are compatible with Slater–Pauling role. The optical treatment of Co₂VGa is different from three other compounds. All mentioned compounds have metallic behavior by 22 eV plasmonic frequency. The imaginary part of the dielectric function for the up spin indicates that the main optical transitions occurred in this spin mode. Moreover, the elastic results show that the Co₂VGa does not have elastic stability, but the other three compounds have fully elastic stability and the Co₂V(Al, Ge and Si) belong to the hardness of materials.

Density functional theory (DFT) and generalized gradient approximation (GGA) have been employed to study origins of the intrinsic $n$-type electrical conductivity in the zinc oxide. Hubbard-like term has been introduced to provide a better description for the Zn 3$d$ electrons. Two intrinsic point defects, namely oxygen vacancy and hydrogen impurity, were taken into consideration. Results on conductivity are analyzed using density of states patterns for different configurations of defects. Microstructure and local magnetic moments are studied as well. The obtained results clearly indicate that oxygen vacancy does not and cannot be responsible for the intrinsic $n$-type electrical conductivity whereas inserted hydrogen atoms tend to lose its only valence electron, which in turn becomes a free electron contributing towards the $n$-type conductivity.

Magnetic and optical properties of (Mn, Fe)-doped SiC nanosheet (NS) are investigated using first principle calculations based on Density Functional Theory (DFT) within the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method. The Generalized Gradient Approximation (GGA) shows that doping SiC NS by Mn has a half-metal ferromagnetic behavior when one Si atom is replaced by Mn or Fe. We also study the effect of (Mn, Fe) doping on optical properties of SiC NS such as absorption coefficient and optical reflectivity as function of energy. We found that doping SiC NS increases the absorption coefficient, the optical conductivity and the reflectivity in the visible region.

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlation term is treated using two approximations spin-polarized local density approximation (LSDA) and spin-polarized generalized gradient approximation generalized (GGA). The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2). The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half-metallic behavior in both phases. The magnetic moment is found to be around 7.0 $\mu$B. The mechanical properties of CmX (X = N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C${}_{𝜗}$ and C${}_P$, the entropy ${𝒮}$ and the Grüneisen parameter $\gamma$ have been foreseen at expanded pressure and temperature ranges.

The structural, electronic, optical properties and band offsets of Co₂VGa/GaAs(001) interfaces are discussed within the framework of density functional theory (DFT) using the FP-LAPW method, and the exchange-correlation potential is approximated by GGA. All interface structures are stable in the energy point of view, however the V–Ga/As case is found to be more stable than the others. A remarkable potential difference ($\mathrm{\Delta }$V) appeared in all the interfaces, so the Co₂VGa/GaAs(001) interfaces are good candidates for electron injection. In all the cases, there is no full spin polarization at the Fermi level, but high CBO and ${\mathrm{\Phi }}_p$ coefficients make them promising candidates for spin injection in the transport devices. Optical studies confirm the high metallic treatment of these interfaces as the main electron transitions had occurred in the infrared and visible regions. The real parts of the dielectric function in the x-direction indicate the different behaviors of “Co–Co/As and V–Ga/Ga” and “Co–Co/Ga and V–Ga/As” in the infrared area. In addition, the plasmon frequencies had occurred at high UV energies.

In this paper, we explore the structural, electronic, thermoelectric and elastic properties of intermetallic compounds ScTM (TM = Cu, Ag, Au and Pd) using density functional theory. The produced results show high values of Seebeck coefficients and electrical conductivity for these materials. High power factor for these materials at room-temperature shows that these materials may be beneficial for low-temperature thermoelectric devices and alternative energy sources. Furthermore, elastic properties of these compounds are also calculated, which are used to evaluate their mechanical properties. The Cauchy’s pressure and B/G ratio figure out that these compounds are ductile in nature. The calculated results also predict that these compounds are stable against deforming force.

Geometric and electronic structures of W${}_m$Mo${}_n$ (m + n$\le$ 7) clusters have been systematically calculated by density functional theory (DFT) at the generalized gradient approximation (GGA) level for ground-state structures. Geometry optimization shows that clusters are almost bipyramid structures with m + n$>$ 4. E${}_b$ of clusters is mainly dominated by W atoms. And the substitution of atoms between W and Mo in Mo${}_n$ or W${}_n$ (n$\le$ 7) clusters enhances the stability of the original clusters. The calculated IE shows that W${}_{1,3,5}$Mo, W${}_{1,3,5}$Mo₂, W${}_{1,2,3}$Mo₃ and WMo${}_{4,5}$ are relatively more stable in the chemical reaction. In addition, the magnetism of clusters mainly comes from valance d orbitals.

In the present work, first-principles calculations were performed to obtain the structural, electronic and optical properties of lithium niobate crystal using two exchange-correlation functionals (GGA-PBE and TB-mBJ). The calculated structural parameters were very close to the experimental values. TB-mBJ functional was found to be good when compared to LDA and GGA functionals in case of bandgap energy of 3.715 eV of lithium niobate. It was observed that the upper valence and lower conduction bands consist mainly the O-2p and Nb-4$d$ states, respectively. Furthermore, calculations for real and imaginary parts of frequency-dependent dielectric function $𝜀(\omega )$ of lithium niobate crystal were performed using TD-DFT method. The ordinary refractive index n${}_o(\omega )$, extraordinary refractive index n${}_e(\omega )$, its birefringence and absorption peaks in imaginary dielectric function ${𝜀}_2(\omega )$ were also calculated.

Electronic, mechanic and lattice dynamic properties of yttrium-based compounds, X₃Y, where X = Pd, Pt and Rh were investigated using the density functional theory. The electronic band calculations demonstrated that X₃Y compounds are metallic at the cubic crystal structures. The calculated elastic constants using the energy-strain method indicate that the three materials are mechanically stable. The calculated bulk modulus and Young’s modulus values suggest that the Pt₃Y is stiffer than that of the other two. The type of bonding and ductility in the X₃Y compounds were also evaluated based on their B/G ratios, Cauchy pressures (C${}_{12}$–C${}_{44}$) and band structure calculations. These compounds were found to be ductile in nature. The density functional perturbation theory was used to derive full phonon frequencies and total and projected phonon density of states. The computed full phonon spectra for X₃Y compounds show that these compounds in the L1₂ phase are dynamically stable. Debye temperature and specific heat of these compounds were also calculated and evaluated using quasi harmonic approximation.

Half-metallic, optical and thermodynamic phase diagrams of two-dimensional Mn₂ZrZ (Z = Ge, Si) have been calculated by density functional theory (DFT) framework with full-potential linear augmented plane-wave (FP-LAPW) method. The spin-polarized electronic computations show that these layers have metallic behavior with a spin polarization less than 100%. It is observed that with increasing thickness of the layers, both the thermodynamic and energy stabilities increased, and the graphene-like layers of Mn₂ZrGe with a thickness of 7.6955 Å and Mn₂ZrSi with a thickness of 7.551 Å are completely stable thermodynamically. The optical responses of Mn₂ZrZ (Z = Ge, Si) have anisotropy at infrared region versus the optical direction and have high metallic nature in this optical range. The plasmonic frequencies have occurred after the visible edge and the refraction index becomes lower than one after the ultra-violet edge.

We have performed the first-principles density functional theory (DFT) and DFT$+$U calculations on the electronic and optical properties of CaO: Eu${}^{+2}$ (SrO: Eu${}^{+2}$) phosphors compounds. Herein, we have focused on the polarization of the electronic structures, i.e., the energy bandgap and the density of states. All electrons were treated within the most common exchange and correlation functional called generalized gradient approximation plus optimized effective Hubbard parameter U as GGA$+$U. GGA$+$U is a very effective tool for describing the electronic band energy upto considerable accuracy. Hence, we have opted for the arbitrary values of U as 3.0, 4.0, 5.0 and 7.0 eV to treat the strongly correlated electrons for obtaining the matching result with the experimental one. However, GGA$+$U is highly expensive in terms of computation due to interaction of d or f electrons. The result shows that the appearance of Eu-4f states at the valance band maximum of the spin-up causes a substantial impact on the electronic properties of the studied compounds. The value of energy bandgap is smaller in case of spin up as compared to spin down case. In case of majority spin, the energy gap of 2.224 (2.14) eV belongs to the Eu-4f orbitals and governs the CBM. The partial densities of states (PDOS) structure displays a strong hybridization that may be pointed to the formation of covalent bonds. The calculated and the measured values are in good agreement with each other. In the study of optical properties of the compound, the optical spectral structure shows a lossless region and uniaxial anisotropy. The value of uniaxial anisotropy is positive at static limit and its value is negative above this value.

The first-principles study of cubic perovskites SmXO₃ (X = Al and Co) for elastic, mechanical and optical properties is done in the framework of density functional theory (DFT). Optimized structural parameters are obtained first to find mechanical and optical properties of the materials. These obtained structural parameters are in accordance with the published data. The cubic elastic parameters C${}_{11}$, C${}_{12}$ and C${}_{44}$ are then calculated by using generalized gradient approximation (GGA) as an exchange correlation functional in Kohn–Sham equations. Poisson’s ratio, shear modulus, Young’s modulus and anisotropic factor are deduced from these elastic parameters. These compounds are found to be elastically anisotropic and SmAlO₃ is brittle while SmCoO₃ is ductile. Their covalent nature is also discussed by using Poisson’s ratio. In addition, optical properties like absorption coefficient, extinction coefficient, energy loss function, dielectric function, refractive index, reflectivity and optical conductivity are studied. This study predicts that SmAlO₃ and SmCoO₃ are suitable for optoelectronic devices.

Ab initio study has been carried out to investigate the band structure, density of state and optical dielectric function of pure and Nitrogen (N)-doped rutile phase of TiO₂. The band structure obtained with the inclusion of U parameter of 8.5 eV compared favorably with experimental result. Bandgap of N-doped rutile decreases with respect to pure rutile which is traceable to 2p state of the Nitrogen dopant as revealed in partial density of state (PDOS). The optical properties calculated revealed that N-doped rutile has at least one optical peak in the visible light region of the electromagnetic spectrum which suggests it to be a potential material for photovoltaic application than pure rutile. Our results suggest that optical properties of rutile can be adapted by doping with Nitrogen at different concentration which enhances its potential as photocatalyst.

First principles investigations of the electronic, optical and thermoelectric performance of RbZn${}_{1-x}$Ni${}_x$F₃ (x = 0, 0.25, 0.5, 0.75 and 1) alloys are calculated using spin polarized full-potential linear augmented plane wave method, as implemented in Wien2k code. These alloys are found to be stable, ductile and can be formed with ferromagnetic character. RbZn${}_{1-x}$Ni${}_x$F₃ are found to be insulator alloys with bandgap energy of range 7.02–5.14 eV using the modified Becke–Johnson functional. This gap is decreasing with increasing the Ni concentration in the unit cell. The optical parameters are calculated in the energy range upto 35 eV. The calculated static refractive index values are found directly proportional with the higher concentration of Ni atoms in the alloys. The transport coefficients are calculated using BoltzTrap code. The hole assumes the main charge carriers of the present alloys with p-type-doping for RbZnF₃ alloy and n-type-doping for RbZn${}_{1-x}$Ni${}_x$F₃. The calculated optical and transport coefficient values show promising optoelectronic and thermoelectric applications of the studied alloys.

We have examined the magnetic stability; antiferromagnetic (AFM) ordering; electronic and magnetic properties of composition XMn₂Y₂ (X = Ca, Sr; Y = Sb, Bi) using framework of full-potential linearized augmented plane wave (FP-LAPW) method within generalized gradient (PBE-GGA) approximations in AFM phase. We have specified that AFM state is most suitable for these compounds as compared to other configurations at their relaxed lattice parameters. An AFM spin configuration of Mn atoms is shown to be impressive state for these compounds. Based on its electronic properties, these compounds have a metallic nature in Paramagnetic (PM) but in AFM phase it shows different nature from PM phase. From a suitable phase, it has been cleared that both Mn atoms well-adjusted antiferromagnetically.

The mechanical, electronic and thermodynamic properties of Pd₃M (M=Sc, Y) compounds have been investigated using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) formalism. The generalized gradient approximation (GGA) is used to treat the exchange–correlation terms. The calculated formation enthalpies and the cohesive energies reveal that the L1₂ structure is more stable than the D0${}_{24}$ one. The obtained lattice parameters and bulk modulus calculations conform well to the available experimental and theoretical results. The elastic and mechanical properties are analyzed and results show that both compounds are ductile in nature. The Debye temperature and melting temperature are also estimated and are in a good agreement with experimental findings. The total and partial densities of states are determined for L1₂ and D0${}_{24}$ structures. The density of states at the Fermi level, $N$($E_{\mathrm{\text{F}}}$), indicates electronic stability for both compounds. The presence of the pseudo-gap near the Fermi level is suggestive of formation of directional covalent bonding. The number of bonding electrons per atom $n_b$ and the electronic specific heat coefficient $\gamma$ are also determined. The quasi-harmonic Debye model has been used to explore the temperature and pressure effects on the thermodynamic properties for both compounds.

The ab initio calculation is performed to investigate about the structural and the electron transport properties of the experimentally reported (parent) compounds viz., BaFe₂As₂, SrFe₂As₂, CaFe₂As₂ and the novel compounds which are anticipated from our computational work namely BaFe₂Bi₂, SrFe₂Bi₂, CaFe₂Bi₂ with different magnetic order. The space group of the reported compounds is I4/mmm (139) and belong to ThCr₂Si₂ type. The formation energies of the reported compounds are compared in the anti-ferromagnetic (AFM), nonmagnetic (NM) and ferromagnetic (FM) orders. From the comparison, it reveals that the anti-ferro magnetism is the stabled state for the reported compounds. At ambient temperature with constant relaxation time, the resistivity, power factor, Seebeck coefficient and electrical conductivity are computed by using BoltzTraP transport theory code. To explain the superconducting nature of the novel compounds the transition temperature (T${}_C$), electron–phonon coupling factor and Debye temperature are calculated and presented. The mechanical stability of the compounds is examined by using Young’s, bulk and shear modulus, anisotropy constant and Poisson’s ratio which are calculated by using Tetra-elastic code. The Mechanical Temperament of these compounds is analyzed by using Pugh’s ratio. The ELATE tool is used to visualize the elastic properties of these compounds. The thermodynamical stability of the compounds is examined by using Gibbs free energy, vibrational Helmholtz free energy and entropy which are calculated by using Gibbs2 code. All the properties of the theoretically predicted (novel) compounds are analyzed and compared with their parent (experimentally reported) compounds.

The structural, electronic, elastic and thermodynamic properties of ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}}$, Al, Ga, In and TI; $\mathrm{\text{X}}=\mathrm{\text{C}}$ and N) phase have been systematically investigated by the first principles. The optimized lattice parameters are in good agreement with the experimental values and better than the available theoretical data. We calculated the elastic constants $C_{ij}$ and the total density of states, which verified mechanical stability and electronic structural stability, respectively. The other elastic parameters including bulk modulus, shear modulus, Young’s modulus, Cauchy pressure, shear anisotropy factor, linear compressibility coefficients, Pugh’s ratio, Poissons’s ratio, microhardness parameter and machinability index are calculated and discussed in this work. The results show that the compounds we studied are stable in mechanics and are anisotropic materials; the compressibility along $c$-axis is lower than that along $a$-direction except for ${\mathrm{\text{V}}}_2\mathrm{\text{BX}}$ ($\mathrm{\text{X}}=\mathrm{\text{C}}$ and N); the compounds of ${\mathrm{\text{V}}}_2\mathrm{\text{AC}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}},\mathrm{\text{Al}},\mathrm{\text{Ga}},\mathrm{\text{TI}}$) and ${\mathrm{\text{V}}}_2\mathrm{\text{AN}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}},\mathrm{\text{Al}},\mathrm{\text{Ga}}$) are brittle in nature, and ${\mathrm{\text{V}}}_2\mathrm{\text{InN}}$ and V₂TIN are ductile in nature; the shear modulus $G$ limits the mechanical stability of the materials under consideration; the ability to resist shape change and the stiffness of ${\mathrm{\text{V}}}_2\mathrm{\text{AC}}$ are stronger compared with ${\mathrm{\text{V}}}_2\mathrm{\text{AN}}$ when A takes B, Al, Ga, In, TI, respectively. Finally we have estimated the Vickers hardness which shows that the hardness of the ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}}$, Al, Ga, In, TI) would decrease when C is replaced by N. At last, we investigated the thermodynamic properties of ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ by calculating the phonon dispersion, Debye temperature and minimum thermal conductivity. The results show that all structures are dynamical stable and the compounds of ${\mathrm{\text{V}}}_2\mathrm{\text{BC}}$, ${\mathrm{\text{V}}}_2\mathrm{\text{BN}}$, ${\mathrm{\text{V}}}_2\mathrm{\text{AlC}}$ and ${\mathrm{\text{V}}}_2\mathrm{\text{AlN}}$ are candidates for thermal barrier coating (TBC) materials.

In this work, Mn${}^{2+}/$Eu${}^{3+}$ co-doped Zn₂GeO₄ (Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+})$ was prepared by high-temperature solid phase method. Compared with common fluorescent materials Zn₂GeO₄:Mn${}^{2+}$, Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ could not only emit strong green fluorescence of 535 nm, but also maintain excellent persistent luminescence performance. Through Density Functional Theory calculation, we obtained the fine band structure of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$. The results of the band structure were consistent with the experimental spectral data. On this basis, we proposed a new luminescence mechanism model of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ to explain the phenomena observed in experiment reasonably, though which was not completely consistent with previous works. When Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ was excited, electron–hole separation occurred in the valence band (VB), and the electron transitioned to the conduction band (CB) directly. Through CB, the electron was trapped by trap levels (⁷F${}_0{\sim }^7$F₅ of Eu${}^{3+})$ and maintained metastable for a long time. Under the action of thermal stimulation, electron returned to CB from the trap level slowly. The electron was captured again by the ⁴T₂(D) level of Mn${}^{2+}$. Then the electron transitioned down toward VB and recombined with the previous hole and emitted a photon with 535 nm (afterglow). The samples were being irradiated, trap levels accommodated the excited electrons to saturation. More electrons excited into the CB could not be captured by the trap levels any more. They were captured directly by the ⁴T₂(D) and transitioned directly to VB, then emitted green fluorescence.

This work is a part of a series of investigations devoted to the study of the relationship between nonlinear optical properties and pseudosymmetric features of some groups of crystal compounds [A. P. Gazhulina and M. O. Marychev, Cryst. Struct. Theory Appl. 2, 106 (2013). doi.org/10.4236/csta.2013.23015; A. P. Gazhulina and M. O. Marychev, J. Alloys Compd. 623, 413 (2015). doi.org/10.1016/j.jallcom.2014.11.028; A. P. Gazhulina and M. O. Marychev, J. Solid State Chem. 239, 170 (2016). doi.org/10.1016/j.jssc.2016.04.034]. Crystals of the wurtzite ($B$4) structural type (45 crystals) have been considered. In the framework of density functional theory, the structural, electronic, linear and nonlinear optical properties were investigated using the full-potential linearized augment plane wave (FP-LAPW) method. The obtained results are compared to available experimental and computational data. Diagrams “Second-order Nonlinear Susceptibility–Degree of Pseudoinversion” at 1.064 and 0.634 $\mu$m wavelengths were constructed.

Using Monte Carlo Basin-hopping algorithm within the Gupta potential, a systematic investigation has been performed for the best chemical ordering structures of 19-atom trimetallic ${\mathrm{\text{Pd}}}_n{\mathrm{\text{Ag}}}_{(17-n)}{\mathrm{\text{Pt}}}_2$ nanoclusters with double icosahedral geometry. The structures with the lowest energy at Gupta level are then re-optimized by DFT relaxations and the DFT relaxations confirmed the lowest energy structures obtained at the Gupta level indicating the double icosahedron structure is favorable for 19-atom ${\mathrm{\text{Pd}}}_n{\mathrm{\text{Ag}}}_{(17-n)}{\mathrm{\text{Pt}}}_2$ nanoclusters. It was observed that the caloric curves exhibit a smoother transition with structural isomerizations other than a sharp jump behavior.

The Half Heusler alloy (HHA) MnCrP has been studied theoretically for structural, elasto-mechanical and phonon properties. The structure is optimized and the calculated structural parameters are close to the literature. This optimized data is used to estimate three independent second-order cubic elastic constants $C_{11}$, $C_{12}$ and $C_{44}$. The mechanical stability criteria are explored by these constants and further used to estimate the elastic moduli; Young’s, bulk and shear modulus. The mechanical parameters like Poisson’s ratio, Pugh’s ratio, anisotropic factor, Cauchy pressure, shear constant, Lame’s constants, Kleinman parameter are also calculated and discussed. Discussions reveal the ductile nature, ionic behavior, anisotropic nature and mechanical stability of MnCrP. The metallic nature, compressibility, stiffness and interatomic forces of material are also described. Furthermore, the Debye temperature, where the collective vibrations shifts to an independent thermal vibrations, is also calculated. Longitudinal and transverse sound velocities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of the alloy as no negative phonon frequencies in the phonon-dispersion curves. These curves are used to estimate the reststrahlen band where light reflects 100% and the suitability of material is checked for Far Infrared (FIR), photographic, optoelectronic devices and sensors.