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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.

The electronic structures and thermal properties of hexagonal XO ($\mathrm{\text{X}}=\mathrm{\text{Be}}$, Mg and Sr) nanosheets are studied within the density functional theory. The thermal properties are computed using the specified structural parameters of the electronic properties. Thermal properties including entropy, enthalpy, free energy and heat capacity for XO nanosheets are reported. It is found that BeO is an insulator, whereas MgO and SrO are semiconductors based on the energy gap value within GGA and HSE06. The electronegativity and bonding nature of XO nanosheets differ, resulting in considerable variations in thermodynamic parameters that follow a similar pattern as a function of temperature. Enthalpy and entropy increase with temperature whereas free energy falls, owing to a change in the binary oxide internal energy of the system and the electron density distribution. Thermal energy absorbed by the lattices grows with increasing temperature to the point at which all of their modes are activated and the systems start to display unharmonicity deviating from a linear dependence. Variable parameter ranges for XO nanosheets are useful in the development of thermoelectric nanodevices.

Edge state and interfacial design are efficient strategies to regulate the spin-transport properties of nanoscale devices. Spin-polarized transport properties of VC₂ nanoribbon device and poly-(terphenylene-butadiynylene) PTB molecular junctions are studied by using density functional theory (DFT) and non-equilibrium Green function. Results show good self-selected filtering properties for spin-up current are highly suppressed, where there is only spin-down current that can propagate through the scattering region of such a nanoribbon device. What needs to be pointed out is that spin-down current exhibits an obvious negative differential resistance effect. Current and transmission spectrum peaks are significantly weakened, and the negative differential resistance effect disappears after a PTB molecule is embedded between two semi-infinite VC₂ nanoribbon electrodes. This work provides a basis for improving the design and method of spintronic devices.

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.

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.

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.

A brief review is presented of the status of quantum chemical studies of porphyrins and related molecules.

This paper reviews the studies on the electronic structures and spectroscopic properties of sandwich-type complexes M(Pc)₂ and M₂(Pc)₃. The subjects discussed are as follows. (1) Electronic spectra of closed-shell Pc dimers and trimers. The complexes with closed-shell systems, such as [Lu(Pc)₂]⁻, Sn(Pc)₂ and Lu₂(Pc)₃, can be thought of as stacked systems composed only of Pc²⁻. The excited states of these complexes can be described by locally excited and charge transfer configurations. The coupling terms of the configurations are written using orbitals localized on each Pc ring. Assignments of the observed absorption bands are discussed. Computational studies on the band assignments were carried out using a localized molecular orbital (LO) basis which maximizes orbital populations on one of the Pc rings. (2) Electronic structures of πelectron-deficient Pc dimers and trimers. Oxidation of [Lu(Pc)₂]⁻ or Lu₂(Pc)₃ yields systems with π-electron deficiency or π-hole(s) residing on multiple Pc sites. The delocalized nature of the π-hole in Lu(Pc)₂ is elucidated by comparison of the electronic spectra of symmetric and asymmetric dimers composed of Pc and Nc(H₂Nc ≡ naphthalocyanine). The band assignments of the dimer radicals are discussed. The Pc trimer radical shows an intense absorption band at about 5000 cm⁻¹, which is 2000 cm⁻¹ lower than the valence resonance band of Lu(Pc)₂. The two-electron-deficient complexes [Lu(Pc)₂]⁺ and [Lu₂(Pc)₃]²⁺ also show intense near-IR bands at higher energy than the corresponding monoradical species. The interactions that determine the excitation energies of the near-IR bands of the π-electron-deficient species are elucidated.

Computational studies exploring the extent to which differences in proximal axial ligands modulate structure, spectra, and function of peroxidases have been performed. To this end, three heme models of compound I were characterized differing only in the axial ligand. The axial ligands considered were L=ImH, Im^-, that are alternative protonation models for a typical peroxidase with an imidazole ligand such as horseradish peroxidase (HRP-I), and L=SCH- that is a model for an unsual peroxidase, chloroperoxidase (CPO-I). Density functional calculations (DFTs) were performed to determine the optimized geometries and electronic structure of each of these three species. Their electronic spectra were also calculated at the DFT optimized geometries, using the INDO/S/CI method. The results of these studies led to the following conclusions: (1) the presence of the nearby Asp in a typical peroxidase does indeed decrease the energy required to deprotonate the imidazole making the two forms essentially degenerate, (2) neither the state of protonation of the imidazole ligand nor the change in axial ligand from an imidazole in typical peroxidases such as HRP to a mercaptide in CPO significantly alters the characteristics of the lowest energy spin state or the electronic structure of compound I in a way that can obviously affect function, (3) both the Im^- and ImH forms of the peroxidase compound I (HRP-I) lead to the same dramatic reduction in intensity relative to the ferric resting form observed experimentally. However, only in the ImH form of HRP-I does the calculated relative shift of one component of the Soret bands relative to CPO-I agree with that observed in the transient spectra of HRP-I compared to CPO-I. These results taken together strongly indicate that factors other than the nature of the proximal axial ligand are the main determinants of function.

The structural and electronic properties of optimized open-ended single-wall carbon nanotubes with zigzag geometry have been investigated. The calculations were performed using molecular mechanics, extended Hückel, and AM1–RHF semiempirical molecular orbital methods. It has been found that the density of states of the zigzag model is sensitive to the tube size and changes as the tube length increases. On the other hand the energetics of the tube shows an almost linear dependence to the tube length, and a converging characteristics with respect to the number of hexagons forming the tube.

An impact of the spin–orbit interaction on the electron quantum confinement is considered theoretically for narrow gap semiconductor cylindrical quantum dots. To study the phenomena for InAs quantum dot embedded into GaAs semiconductor matrix, the effective one electronic band Hamiltonian, the energy position dependent electron effective mass approximation, and the spin-dependent Ben Daniel–Duke boundary conditions are considered, formulated and solved numerically. To solve the nonlinear Schrödinger equation, we propose a nonlinear iterative algorithm. This calculation algorithm not only converges for all simulation cases but also has a good convergent rate. With the developed quantum dot simulator, we study the effect of the spin–orbit interaction for narrow gap InAs/GaAs semiconductor cylindrical quantum dots. From the numerical calculations, it has been observed that the spin–orbit interaction leads to a sizeable spin-splitting of the electron energy states with nonzero angular momentum. Numerical evidence is presented to show the splitting result is strongly dependent on the quantum dot size.

We investigate boron and nitrogen substitutional doping single wall carbon nanotubes (SWCNTs) by first-principles calculations. The optimized geometres of boron and nitrogen substituted SWCNTs exhibit bamboo-like structures. Boron and nitrogen impurities form acceptor and donor states in semiconductor SWCNTs. The highest occupied molecular orbital (HOMO) indicates the trend of forming inter-tube bonds in doping SWCNTs. It may start a new way to form inter-tube bonds by doping in SWCNTs.

We present here an optimized and parallelized version of the augmented space recursion code for the calculation of the electronic and magnetic properties of bulk disordered alloys, surfaces and interfaces, either flat, corrugated or rough, and random networks. Applications have been made to bulk disordered alloys to benchmark our code.

The electronic structure and linear optical properties of luminescent material EuKNaTaO₅ are investigated by employing full-potential linear augmented plane wave method. Our results show highly localized Eu4f states which pinned in the energy range below the unoccupied Ta5d states and over the occupied O 2p states. The optical spectra are analyzed and interpreted in terms of the electronic structure. It is found that Eu ions absorb the major parts of the incident energy below 3.3 eV. This is in accordance with the experimental result that EuKNaTaO₅ phosphor is efficient under the excitation of 535 nm (2.3 eV) visible part of the spectrum. The linear optical properties are found to be anisotropic.

A density functional study for structural and electronic properties of Zinc Oxide (ZnO), in wurtzite, rock salt and zinc-blende phases has been performed using full potential-linearized augmented plane wave/linearized augmented plane wave plus local ideal orbital (FP-LAPW/L(APW+lo) approach as realized in WIEN2k code. To approximate exchange correlation energy and corresponding potential, a special GGA parameterized by Wu–Cohen has been implemented. Our results of lattice constants, bulk moduli as well as for internal parameter with GGA-WC are found to be more reliable. This study reveals that value of internal parameter decreases with increasing volume whereas computed electronic band structure confirms the direct band gap behavior of ZnO in B4 and B3 phases while indirect band gap behavior in B1 phase. Moreover, two fold degeneracy at the maxima of valence band for B4 and B1 phases whereas three fold for B3 is observed. A detailed comparison with experimental and other first principles studies is also made.

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).

Topological insulators (TI) are immensely investigated due to their promising characteristics for spintronics and quantum computing applications. In this regard, although bismuth, telluride, selenide and antimony containing compounds are typically considered as topological insulators, materials with Hg₂CuTi-type structure have also shown their potential for TIs as well. Here, we present first principles study of the Y₂RuPb compound, pertaining to its structural, mechanical, electrical and the optical properties. Calculations are executed at the level of the parameterized Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA), employing the full-potential (FP) linearized muffin-tin orbital (LMTO) approach, as designed within the density functional theory (DFT). The study is carried out on the Hg₂CuTi-type and Cu₂MnAl-type structures of the Y₂RuPb compound. From our structural calculations, it is found that Y₂RuPb is more stable in its Hg₂CuTi-type structure; however, the analysis of the mechanical properties reveals its stability in both phases against any kind of elastic deformation. Similarly, Dirac cone shaped surface energy levels found in the predicted electronic band structure of the Y₂RuPb compound, and good agreement of the obtained results with Zhang et al., demonstrates that it is a topological insulating material. Additionally, the real and imaginary parts of the dielectric function $\epsilon$ ($\omega$) and refractive index n ($\omega$), for an energy range up to 14eV, are analyzed as well.

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.