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In this research work, a study on the structural, optoelectronic, and thermodynamics propertiesof the SnZrCH3 (CH = S, Se) compounds is presented. The study is performed by the “full potential linearized augmented plane wave plus local orbitals (FP-(LAPW + lo)) method framed within density functional theory (DFT). To treat with exchange-correlation energy/potential, different approximations; local density approximation (LDA), generalized approximation (GGA) by Wu and Cohen (WC) named as (WC-GGA) are used toestimate structural properties such as lattice constants, bulk moduli,and related results of pressure derivative.Besides that Engel Vosko's approach of GGA named as (EV-GGA) and Becke-Johnson modified form of exchange-correlation potential (mBJ-GGA) is also used to obtain reliable results of the electronic and optical properties. Our calculations of electronic band structures and density of states endorse both compounds of indirect bandgapnature withbandgap energy 1.054 eV and 0.531 eV for SnZrS3 and SnZrSe3, respectively at the level ofmBJ-GGA. Our calculations of the optical absorption parameters show the highest values of absorption coefficients in the ultraviolet (UV) region, attributed to localized Zirconium states lying in the lower region of the conduction band. Hence, our findings show that both SnZrS3 and SnZrSe3 compounds are potential candidates for photovoltaic applications.Moreover, the pressure effects on the lattice constants, heat capacities, thermal expansion coefficients, entropy, and Debye temperature are also explored using the quasi-harmonic Debye model.

We performed ab initio calculations using the FPLAW method with the local density approximation (LDA) implemented in the WIEN2 k code for the orthorhombic (α) and triclinic (β) phases of BiNbO4. The modified Becke–Johnson exchange potential (mBJ)-LDA approach was also used to improve the electronic properties. The lattice constants calculated for both structures using the LDA are in good agreement with the experimental values. For the band structure calculations, the mBJ-LDA approach provides reasonable agreement for the band gap value compared with the LDA. The estimated (mBJ)-LDA band gap values are 2.89 eV (3.73 eV) and 2.62 eV (3.15 eV) for the α and β phases of BiNbO4, respectively. Significant optical anisotropy is clearly observed in the visible-light region. We also calculated and evaluated the electron energy loss spectrum for BiNbO4. This work provides the first quantitative theoretical prediction of optical properties and electron energy loss spectra for both the orthorhombic and triclinic phases of BiNbO4.

The structural, elastic, and thermodynamic properties of the cubic anti-perovskite $$\hbox {RBRh}_{3}$$ (R = Sm, Eu, Gd, and Tb) compounds have been investigated using first principles full-potential augmented-plane wave plus local orbitals (FP-APW+lo) method with the generalized gradient approximation. The ground-state quantities such as the lattice parameter, bulk modulus, and its pressure derivative, as well as elastic constants are estimated. Computed equilibrium lattice constants agree well with the available experimental data. The full set of first-order elastic constants and their pressure dependence, which have not been calculated or measured yet, have been determined. The elastic moduli increase linearly with increasing pressure and satisfy the generalized elastic stability criteria for cubic crystals under hydrostatic pressure. The shear modulus, Young’s modulus, and Poisson’s ratio are calculated for ideal polycrystalline $$\hbox {RBRh}_{3}$$ aggregates. The Debye temperature is estimated from the average sound velocity. From the elastic parameter behavior, it is inferred that cubic anti-perovskites $$\hbox {RBRh}_{3}$$ are ductile in nature and that the bonding is predominantly of an ionic nature. Following the quasi-harmonic Debye model, the temperature effect on the lattice constant, bulk modulus, heat capacity, and Debye temperature is calculated reflecting the anharmonic phonon effects.

The mechanical, optoelectronic, and thermodynamic properties of carbon silicon nitride spinel compound have been investigated using density functional theory. The exchange–correlation potential was treated with the local density approximation (LDA) and the generalized gradient approximation of Perdew–Burke and Ernzerhof (PBE-GGA). In addition, the Engel–Vosko generalized gradient approximation (EV-GGA) and the modified Becke–Johnson potential (TB-mBJ) were also applied to improve the electronic band structure calculations. The ground state properties, including lattice constants and bulk modulus, are in fairly good agreement with the available theoretical data. The elastic constants, Young’s modulus, shear modulus, and Poisson’s ratio have been determined by using the variation of the total energy with strain. From the elastic parameters, it is inferred that this compound is brittle in nature. The results of the electronic band structure show that CSi2N4 has a direct energy band gap (Γ–Γ). The TB-mBJ approximation yields larger fundamental band gaps compared to those of LDA, PBE-GGA, and EV-GGA. In addition, we have calculated the optical properties, namely, the real and the imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, and energy loss function for radiation up to 40.0 eV. Using the quasi-harmonic Debye model which considers the phononic effects, the effect of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and the heat capacity for this compound were investigated for the first time.

We have performed first-principle calculations using the full-potential linear augmented plane wave (FP-LAPW) method within density functional theory (DFT) to investigate the structural, elastic and thermodynamic properties of the cubic perovskite RBRh3 (R = Sc, Y and La) compounds. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Single-crystal elastic constants are calculated using the total energy variation versus strain technique, then the shear modulus, Young's modulus, Poisson's ratio and anisotropic factor are derived for polycrystalline RBRh3 using the Voigt–Reuss–Hill approximations. Analysis of the calculated elastic constants and B/G ratios shows that these compounds are mechanically stable and ductile in nature. Using the quasi-harmonic Debye model, the effect of pressure P and temperature T on the lattice parameter a 0, bulk modulus B 0, thermal expansion coefficient α, Debye temperature and the heat capacity C v ...

The structural, elastic and electronic properties of Ti 2 InC and Ti 2 InN compounds have been calculated using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange and correlation potential is treated by the local density approximation (LDA). The calculated ground state properties, including, lattice constants, internal parameters, bulk modulus and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. The effect of pressure, up to 40 GPa, on the lattice constants and the internal parameters is also investigated. Using the total energy-strain technique, we have determined the elastic constants Cij, which have not been measured yet. The band structure and the density of states (DOS) show that both materials have a metallic character and Ti 2 InN is more conducting than Ti 2 InC . The analysis of the site and momentum projected densities shows that the bonding is achieved through a hybridization of Ti -atom d states with C ( N )-atom p states. Otherwise, it has been shown that Ti – C and Ti – N bonds are stronger than Ti – In bonds.

In this work we use the full potential linearized augmented plane wave (FPLAPW) method within the local spin density approximation. Our goal is to study the structural, electronic and magnetic properties of the ferromagnetic CdMnTe and ZnMnTe semiconductors alloys in its ordered chalcopyrite phases (50% of Mn). We have investigated the lattice parameters, bulk moduli, band structures, total and partial densities of states. The determined exchange constants N 0 α (conduction band) and N 0 β (valence band) somewhat agree with a typical magneto-optical experiment. In these systems the s(p)-d exchange interaction between free electrons (holes) and localized magnetic moments plays an important role for their characteristic properties. Our results show that the localization of the Mn spin-majority states are positioned near the top of the valence band and strongly hybridized with it. Furthermore, calculations predict that the p–d hybridization reduces the local magnetic moment of Mn from its free space of 5– 4.32 μ B for Cd 0.5 Mn 0.5 Te and 4.23 μ B for Zn 0.5 Mn 0.5 Te .

Using the first principles full-potential linearized augmented plane-wave method within the local density approximation, we have studied the structural, electronic and optical properties of Ga 2 O 3 in its ambient, monoclinic (β) and high-pressure hexagonal (α) phases. It is found the both β-Ga 2 O 3 and α-Ga 2 O 3 have an indirect band gap. The conduction band minimum (CBM) is located at Γ point for both phases, whereas the valence band maximum (VBM) is located at the M point for β-Ga 2 O 3 and at L point for α-Ga 2 O 3 . The calculated total and partial density of states are also presented. The analysis of the electron charge density shows that the Ga–O bonds have significant ionic character. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. For the monoclinic phase, it is shown that the component with y -direction are more pronounced than that along the x and z .

The ground state electronic structure of wurtzite AlN, GaN, and InN has been calculated using full-relativistic all-electron full-potential linearized-augmented plane-wave method. Several DFT exchange-correlation functionals, including the recently proposed non-empirical meta-generalised gradient approximation (Meta-GGA) have been used. The role played by relativistic effects and meta-GGA functional on the band structures and the density of states is discussed. We find that the meta-GGA improves the accuracy of the structural properties as well as the energies of the semicore d states in both GaN and InN. This new functional slightly outperforms the local density approximation (LDA) and the generalized gradient approximation (GGA) overall as to lattice parameters, bulk modulus, and valence band widths. We find also that the meta-GGA induced modifications of the band structure are significant, but limited to the valence band states, while leaving all other features identical to LDA and GGA calculations. Finally, our results show that GaN and InN present anomalous dependence of the valence band splitting versus pressure.

In this paper, we focus on the role played by the relativistic and d-electron effects on the electronic structure of both wurtzite (a-InN), as well as the zinc-blende (β-InN) modifications of indium nitride. Here we perform all-electron full-potential linearized-augmented plane-wave calculations with spin-orbit interaction. The In 4d electrons are treated both as core and as valence electrons. We compare the performance of the local-density approximation (LDA), the generalized gradient approximation (GGA) and the recently proposed non-empirical meta-generalized gradient approximation (Meta-GGA) in calculations of the structural and electronic properties of InN. Band structures, densities of states, orbital-resolved densities of states, charge densities and ionicity factors are analyzed in great detail. The calculated values of the energy gaps, bandwidths, spin-orbit and crystal-field splittings and the correct band degeneracies are compared to experimental and/or ab-initio results. The role played by relativistic effects and meta-GGA functional on the band structure is discussed. For the structural properties meta-GGA is more accurate and gives the best description of InN. We found that several features of α-InN resemble those of β-InN. Most of the calculated band parameters, of band gaps, total valence bandwidths for α-InN are close to those of P-InN to within 1%. The charges distributions have similar features meaning that this material has the same ionicity factor in both structures even when In 4d states were treated both as core and as valence electrons.

LMSSM, Dpartement de Physique, Facult des Sciences, Universit de Sidi-Bel-Abbs,22000 Sidi-Bel-Abbs, AlgrieReceived 3 March 2002, revised 23 September 2002, accepted 26 September 2002Published online 13 February 2003PACS 71.15.Ap, 71.15.Mb, 71.20.NrWe investigate the electronic properties of the technologically important wide-band-gap semiconductorGaN employing ‘state-of-the-art’ DFT-LDA calculations using a FP-LAPW code. The Ga 3d electronsare treated both as core or as valence electrons and the wurtzite as well as the zincblende modificationsof GaN are investigated. In particular, we address the influence of the lattice configuration and of the delectrons to the electronic structure of w-GaN and c-GaN. Band structures, densities of states, orbital-resolved densities of states, total and partial valence charge densities, and ionicity factors are analysedin great detail. The calculated values of the energy gaps, bandwidths, spin–orbit, crystal-field splittings,and the correct band degeneracies are compared to experimental and/or ab initio results. Several fea-tures of w-GaN resemble those of c-GaN. Most of the calculated band parameters, of band gaps, totaland upper-valence bandwidths, and antisymmetric gap for w-GaN are close to those of c-GaN within1%. The charge distributions have similar features meaning that this material has the same ionicityfactor with or without Ga 3d hybridization in both structures. By examining the pressure dependence ofthe energy band gaps, the value of the hydrostatic deformation potential of the band gap has also beencalculated.

Using the first principles full-potential linearized augmented plane-wave method within the local density approximation, we have studied the structural, electronic and optical properties of Ga 2 O 3 in its ambient, monoclinic (β) and high-pressure hexagonal (α) phases. It is found the both β-Ga 2 O 3 and α-Ga 2 O 3 have an indirect band gap. The conduction band minimum (CBM) is located at Γ point for both phases, whereas the valence band maximum (VBM) is located at the M point for β-Ga 2 O 3 and at L point for α-Ga 2 O 3 . The calculated total and partial density of states are also presented. The analysis of the electron charge density shows that the Ga–O bonds have significant ionic character. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. For the monoclinic phase, it is shown that the component with y -direction are more pronounced than that along the x and z .

This work deals with the electronic properties, in different crystal phases, of AlN (wurtzite and zincblende) compounds computed using an all electron ab initio linearized augmented plane wave method. Results include band structure, total and partial density of states, charge density and the ionicity factor. Most of the calculated band parameters, of direct bandgap, total- and upper-valence bandwidths and antisymmetric gap for wurtzite-AlN are close to those of c-AlN to within 1%. The charge distributions have similar features, meaning that AlN has the same ionicity factor in both structures.