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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 ab initio studies of isomers clearly show the delicate change from sp³ carbon to sp² carbon inside two five-membered rings of these structures, as analyzed by both geometry and electron delocalization of adjacent bonds next to both rings. Electronic origin of 2- with the highest energy among isomers is attributed to the relative increase in orbital energies, localized spatial feature due to lone pairs of chlorines, and π* characteristics for corresponding molecule orbitals. The steric effect not only favors fluorine over phenyl in substituting Cl connected with the 2-C, but also predominates configurations of double-substituted isomers. This work suggests that C_s-C₆₀Cl₆ can serve as one practical substituting template for synthesizing C_s-C₆₀F₆.

Very little information is available about the structural properties of III-nitride binary compounds in the rock-salt phase. We report/review a comprehensive theoretical study of structural properties of these compounds in rock-salt, zinc-blende and wurtzite phases. Calculations have been made using full-potential linearized augmented plane wave plus local orbitals (FP-L(APW+lo)) method as embodied in WIEN2k code framed within density functional theory (DFT). In this approach of calculations, local density approximation (LDA) [J. P. Perdew and Y. Wang, Phys. Rev. B45 (1992) 13244] and generalized gradient approximation (GGA) [J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett.72 (1996) 3865] have been used for exchange-correlation energy and corresponding potential. Calculated results for lattice constants, bulk modulus, its pressure derivative and cohesive energy of these compounds are consistent with the experimental results. Following these calculations, besides many new results for the rock-salt and other phases, a comprehensive review of the structural properties emerges. We also list some peculiar features of these compounds.

CrO₂ has a wide band gap for "down" spins and the Fermi level lies in the middle of the band gap. Calculations based on the local-spin density approximation (LSDA) has been performed to investigate the electronic and physical properties of CrO₂ in the rutile structure (P42/mnm). We considered the semicore electrons as valence electrons and found that CrO₂ appears to be half-metallic with a direct band gap of 1.8 eV in spin-down and has metallic behavior in spin-up configurations.

We hereby are reporting the transition pressure at which lithium fluoride (LiF) compound transforms from direct band gap to indirect band gap insulator on the basis of FP-LAPW calculations. The fundamental band gap of LiF compound suffers direct to indirect transition at a pressure of 70 GPa. The study of the pressure effect on the optical properties e.g. dielectric function, reflectivity, refractive index and optical conductivity of LiF in the pressure between 0–100 GPa, shows that this pressure range is very critical for LiF compound as there are significant changes in the optical properties of this compound.

In this paper, we present ab initio calculations within density functional theory (DFT) to investigate structure, electronic and magnetic properties of Ru₂CrZ (Z = Si, Ge and Sn) full-Heusler alloys. We have used the developed full-potential linearized muffin tin orbitals (FP-LMTO) based on the local spin density approximation (LSDA) with the PLane Wave expansion (PLW). In particular, we found that these Ruthenium-based Heusler alloys have the antiferromagnetic (AFM) type II as ground state. Then, we studied and discussed the magnetic properties belonging to our different magnetic structures: AFM type II, AFM type I and ferromagnetic (FM) phase. We also found that Ru₂CrSi and Ru₂CrGe exhibit a semiconducting behavior whereas Ru₂CrSn has a semimetallic-like behavior as it is experimentally found. We made an estimation of Néel temperatures (T_N) in the framework of the mean-field theory and used the energy differences approach to deduce the relevant short-range nearest-neighbor (J₁) and next-nearest-neighbor (J₂) interactions. The calculated T_N are somewhat overestimated to the available experimental ones.

In this paper, we have carried out a theoretical investigation on the structural and optoelectronic properties of NaCl under pressure effect via first principle calculations within the density functional theory. The structural phase transition from NaCl(B1) to CsCl(B2)-type structures is determined. The compound has a very wide bandgap in both phases. Optical properties including the absorption coefficient, optical conductivity and frequency dependent reflectivity are explained to characterize the optical nature of NaCl up to pressure of 134 GPa.

In this paper, we investigate the structural stability of silicane and germanane under biaxial strain by employing the lattice dynamics calculations within the frame of density functional theory. Our results show that silicane and germanane become unstable even under 1% compressive strain, while maintaining stable under tensile strain. Further calculations about the thermodynamical properties of silicane and germanane show that the phonon contribution to Helmholtz free energy, entropy and specific capacity are insensitive to the tensile strain.

In this paper, the structural, electronic and optical properties of V-doped single-walled ZnO nanotube (8, 0) (SWZnONT (8, 0)) were investigated by the first principles. The calculated formation energy shows that V-doped SWZnONT (8, 0) is more stable than pure SWZnONT (8, 0). Our results show that pure SWZnONT (8, 0) has a direct bandgap about 1.443 eV in Γ point. In the V-doped SWZnONT (8, 0), some bands in both spin down and up cross the Fermi level and the calculated total spin magnetic momentum was obtained about 2.345 μ_B. So we expect that the V-doped SWZnONT (8, 0) exhibits magnetic and metallic behavior. These results are in agreement with other theoretical works. The optical properties such as dielectric function, energy loss function, optical conductivity, refractive index and reflectivity are calculated. Redshift, metallic behavior and anisotropic property were observed in the V-doped SWZnONT (8, 0). Our results suggest that the V-doped SWZnONT (8, 0) can be used in magneto-optical devices. The results showed that the reflectivity of pure and V-doped SWZnONT (8, 0) in the wide energy range is low, therefore, pure and V-doped SWZnONT (8, 0) can be used in transparent coating.

Adsorption of molecular oxygen with a triplet ground state on Fe-, Co-, Ni-, Ru-, Rh-, Pd-, OS-, Ir- and Pt-doped graphene is studied using density functional theory (DFT) calculations. The calculations show that O₂ molecule is chemisorbed on the doped graphene sheets with large adsorption energies ranging from -0.653 eV to -1.851 eV and the adsorption process is irreversible. Mulliken atomic charge analysis of the structure shows that charge transfer from doped graphene sheets to O₂ molecule. The amounts of transferred charge are between 0.375e^- to 0.650e^-, indicating a considerable change in the structures conductance. These results imply that the effect of O₂ adsorption on transition metal-doped graphene structures can alter the possibility of using these materials as a toxic-gas (carbon monoxide, hydrogen fluoride, etc.) sensor.

Structural and magnetic properties as well as the electronic structures of ${\mathrm{\text{Ru}}}_2\mathrm{\text{YGe}}(\mathrm{\text{Y}}=\mathrm{\text{Cr}},\mathrm{\text{Mn}})$ Heusler alloys were investigated in the framework of first principle calculation. Using the full-potential linearized augmented plane wave (FP-LAPW) in connection with the generalized gradient approximation (GGA) treatment of exchange-correlation energy, we have performed the structural optimization in the non-magnetic (NM) and three different magnetic configurations: FM, AFM-I and AFM-II. We have found that our two compounds are stable for the AFM-II state, which agree with the available experimental and theoretical results. The exchange constants $J_1$ and $J_2$ as well as the temperature of transition to the paramagnetic state $(T_N)$ were estimated here by the use of the energy difference method and the mean field approximation. The electronic structure of our compounds in their magnetic state was also studied. The GGA + U method has also been used to take into account the strong correlations among the d orbitals of $\mathrm{\text{Ru}},\mathrm{\text{Cr}}$ and $\mathrm{\text{Mn}}$ atoms. This has considerably improved both the electronic and magnetic results which became close to the corresponding experimental data. We have finally studied the thermodynamic properties using the quasi-harmonic Debye model as implemented in the Gibbs Program.

Our calculations were conducted within density functional theory (DFT) and density functional perturbation theory (DFPT) using norm-conserving pseudo-potential and the local density approximation. The elastic constants of ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$ were calculated, $C_{11}$, $C_{33}$ and $C_{44}$ increase with the increase of Be content, whereas the $C_{12}$ shows a non-monotonic variation and $C_{13}$ decreases when Be concentration increases. The values of bulk modulus $B$, Young’s modulus $E$ and shear modulus $G$ increase with the increase of Be content. Poisson’s ratio $\sigma$ decreases with increased Be concentration. The ductility decreases with increasing Be concentration and the compressibility for ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$ along $c$-axis is smaller than along $a$-axis. Phonon dispersion curves show that ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$ is dynamically stable (no soft modes). Quantities such as refractive index, Born effective charge, dielectric constants and optical phonon frequencies were calculated as a function of the Be molar fraction $x$. The agreement between the present results and the known data that are available only for ZnO and BeO is generally satisfactory. Our results for ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$$(0<x<1)$ are predictions.

In this paper, some optical properties of pure and transition metal-doped (TM = Co and V) single-walled ZnO nanotubes (8,0) (SWZnONT(8,0)) such as, real and imaginary parts of the dielectric function, optical conductivity, refractive index and optical reflectivity, were investigated. The calculations have been performed within framework of the density functional theory (DFT) using the full potential linearized augmented plane wave (FP-LAPW) and the generalized gradient approximation (GGA). The results show that, optical properties of SWZnONT(8,0) are anisotropic, especially at low energies and this anisotropy at low energies increases with doping of V in SWZnONT(8,0) while the Co-doped SWZnONT(8,0) behaves like pure SWZnONT(8,0). Doping of ZnO nanotubes has a significant impact on the value of the dielectric constant, so that due to the presence of V atom, the dielectric constant is increased up to three times. Study of the imaginary part of the dielectric function and optical conductivity showed that the important energy range for absorption processes and optical transitions is low energy range to 15 eV. The optical transitions have been studied based on band structure and density of states. The results of the optical reflectivity showed that these nanotubes are transparent in a wide energy ranges which provide them for using in transparent coatings. In addition, due to the reported magnetic properties for V- and Co-doped ZnO nanotubes, these nanotubes are suitable for using in spintronics and magneto-optic devices.

This paper studies the mechanical properties of polyethylene (PE)–Single-walled carbon nanotube (SWCNT) complexes by using density functional theory (DFT). At the PBE/SVP level, the Young’s modulus of the complexes is obtained as a function of PE content. It is established that, with increasing number of PE chains attached to the SWCNTs, the Young’s modulus monotonically decreases. The density of states (DOS) results show that no orbital hybridization exists between the PE chains and nanotubes. The results of this work are of importance for the design of composite materials employing SWCNTs.

The structural and elastic properties of neutral and ionized dichlorocarbene (CCl₂) functionalized single-walled carbon nanotubes (SWCNTs) were studied using density functional theory (DFT). The Young’s modulus of ionized pristine SWCNTs is found to decrease in comparison to that of neutral models. The interesting effect of increase in Young’s modulus values of ionized functionalized SWCNTs is observed. We ascribe this feature to the concurrent processes of the bond elongation on ionization and the local deformation on cycloaddition. The strong dependence of the elasticity modulus on the number of addends is also observed. However, the CCl₂-attached SWCNTs in their neutral and ionized forms remain strong enough to be suitable for the reinforcement of composites. In contrast to the elastic properties, the binding energies do not change significantly, irrespective of CCl₂ coverage.

In virtue of the particle swarm optimization (PSO) algorithm, the global minimum candidate structures with the lowest energy for ${({\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4)}_n(n=1-3)$ clusters were obtained by first-principles structural searches. The geometric structures and spin configurations of three cationic ${({\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4)}_n^{+}(n=1-3)$ clusters have been identified for the first time by comparing the experimental IR spectra with the calculated results from density functional theory by using different exchange-correlation functionals. It is found that the lowest energy structures of these clusters are of a shape of hat, boat and tower, respectively, with a ferrimagnetic arrangement of spins, and M06L functional is more suitable for ${\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4$ clusters than other ones.

The enhanced photocatalytic activity of tungsten trioxide (WO₃) has been observed experimentally via doping with S element as different dopant types. Herein, a comparative study on the effect of different types of S dopant and native vacancy defects on the electronic structure and optical properties of WO₃ is presented by using hybrid Heyd–Scuseria–Ernzerhof 2006 (HSE06) density functional methods. Six possible models (S${}_{\mathrm{\text{O}}}$–WO₃, S${}_{\mathrm{\text{W}}}$–WO₃, V${}_{\mathrm{\text{O}}}$–WO₃, V${}_{\mathrm{\text{W}}}$–WO₃, S${}_{\mathrm{\text{O}}}$ + V${}_{\mathrm{\text{W}}}$–WO₃ and S${}_{\mathrm{\text{W}}}$ + V${}_{\mathrm{\text{O}}}$–WO₃) based on WO₃ are tentatively put forward. It is found that cationic S doping (the substitution of W by S) is more favorable than anionic S doping (replacing O with S), and both cases become easier to form as native vacancy defect is accompanied. The electronic structures of doped WO₃ depend on the type of dopant: anionic S doping results into three isolated levels in the upper part of valence band, while cationic S doping only induces an effective band gap reduction, which is critical for efficient light-to-current conversion. Interestingly, the isolated states near gap of WO₃ would appear as long as native vacancy defects exist. The introduced levels or reduced band gaps make the systems responsed to the visible light, even further to a range of 400–700 nm. These findings can rationalize the available experimental results and pave the way for developing WO₃-based photocatalysts.

This is an ab initio study instituted on the density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) calculations that are performed to analyze the mechanical, electronic, optical and thermoelectric properties of the cubic MCoF₃ compound (M = K and Rb). The studied compounds are found thermodynamically and mechanically stable. Moreover, these compounds are found to be elastically anisotropic and ductile. KCoF₃ and RbCoF₃ are classified as half-metallic and anti-ferromagnetic compounds. The optical properties are investigated from the dielectric function for the different energy ranges. The thermoelectric properties such as transport properties are determined as a function of temperature using BoltzTrape code in the range of 20–800 K. The present compounds are found to have p-type character. Also, the majority charge carriers are found to be electrons rather than hole. Useful mechanical, spintronic, optical and thermoelectric applications are predicted based upon the calculations.

The electronic structure, density of states (DOS), effective mass are calculated for tetragonal TlInSe₂ from first principle in the framework of density functional theory (DFT). The electronic structure of TlInSe₂ has been investigated by Quantum Wise within GGA. The calculated band structure by Hartwigsen–Goedecker–Hutter (HGH) pseudopotentials (psp) shows both the valence band maximum and conduction band minimum located at the T point of the Brillouin zone. Valence band maximum at the T point and the surrounding parts originate mainly from 6s states of univalent Tl ions. Bottom of the conduction band is due to the contribution of 6p-states of Tl and 5s-states of In atoms. Calculated DOS effective mass for holes and electrons are $m_{{\mathrm{\text{DOS}}}_h}^{\ast }=0.830m_e$, $m_{{\mathrm{\text{DOS}}}_h}^{\ast }=0.492m_e$, respectively. Electron effective masses are fairly isotropic, while the hole effective masses show strong anisotropy. The calculated electronic structure, density of states and DOS effective masses of TlInSe₂ are in good agreement with existing theoretical and experimental results.