Structural, electronic and optical properties of SrCl2 under hydrostatic stress

The results of first-principles theoretical study of the structural, electronic and optical properties of SrCl₂ in its cubic structure, have been performed using the full-potential linear augmented plane-wave method plus local orbitals (FP-APW+lo) as implemented in the WIEN2k code. In this approach both the local density approximation (LDA) and the generalized gradient approximation (GGA) are used for the exchange-correlation (XC) potential. Also we have used the Engel-Vosko GGA formalism, which optimizes the corresponding potential for band structure calculations. We performed these calculations with and without spin-orbit interactions. Including spin-orbit coupling cause to lifts the triple degeneracy at Γ point and a double degeneracy at X point. Results are given for structural properties. The pressure dependence of elastic constants and band gaps are investigated. The dielectric function, reflectivity spectra and refractive index are calculated up to 30 eV. Also we calculated the pressure and volume dependence of the static optical dielectric constant.     

First-principles calculations of structural, elastic, electronic and optical properties of the antiperovskite AsNMg3

The density functional theory (DFT) calculations of structural, elastic, electronic and optical properties of the cubic antiperovskite AsNMg₃ has been reported using the pseudo-potential plane wave method (PP-PW) within the generalized gradient approximation (GGA). The equilibrium lattice, bulk modulus and its pressure derivative have been determined. The elastic constants and their pressure dependence are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus and Poisson's ratio for ideal polycrystalline AsNMg₃ aggregate. We estimated the Debye temperature of AsNMg₃ from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of AsNMg₃ compound, and it still awaits experimental confirmation. Band structure, density of states and pressure coefficients of energy gaps are also given. The fundamental band gap (Γ-Γ) initially increases up to 4 GPa and then decreases as a function of pressure. Furthermore, the dielectric function, optical reflectivity, refractive index, extinction coefficient, and electron energy loss are calculated for radiation up to 30 eV. The all results are compared with the available theoretical and experimental data.     

FP-LMTO method to calculate the structural,thermodynamic and optoelectronic properties of SixGe1−xC alloys

The structural and electronic properties of the ternary Si_xGe_1?xC alloys have been calculated using the full-potential linear muffin-tin-orbital (FP-LMTO) method based on density functional theory within both local density approximation (LDA) and generalised gradient approximation (GGA). The calculated equilibrium lattice constants and bulk moduli are compared with previous results. The concentration dependence of the electronic band structure and the direct and indirect band gaps are investigated. Using the approach of Zunger and co-workers, the microscopic origins of the band gap bowing are investigated also. Moreover, the refractive index and the optical dielectric constant for Si_xGe_1?xC are studied. The thermodynamic stability of the alloys of interest is investigated by means of the miscibility. This is the first quantitative theoretical prediction to investigate the effective masses, optical and thermodynamic properties for Si_xGe_1?xC alloy, and still awaits experimental confirmations.     

Electronic and optical properties under pressure effect of alkali metal oxides

We report results of first-principles calculations for the electronic and optical properties under pressure effect of Li₂O, Na₂O, Ki₂O and Rb₂O compounds in the cubic antifluorite structure, using a full relativistic version of the full-potential augmented plane-wave plus local orbitals (FP-APW+lo) method based on density functional theory, within the local density approximation (LDA) and the generalized gradient approximation (GGA). Moreover, the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is also used for band structure calculations. The calculated equilibrium lattices and bulk moduli are in good agreement with the available data. Band structure, density of states, and pressure coefficients of the fundamental energy gap are given. The critical point structure of the frequency dependent complex dielectric function is also calculated and analyzed to identify the optical transitions. The pressure dependence of the static optical dielectric constant is also investigated.     

Electronic,structural and magnetic properties of TbO under pressure: FP-LAPW study

ABSTRACT

Using the framework of the density functional theory, we calculated electronic, magnetic and structural properties of terbium oxide (TbO) in rocksalt (RS), cesium chloride (CsCl) and zincblende (ZB). Full potential linearized augmented plane wave (FP-LAPW) method within the local spin density approximation (LSDA) and generalized gradient (PBE-GGA) approximations are used. Magnetic and non-magnetic calculations are performed and a modified version of Becke and Johnson (mBJ) exchange potential has been used to calculate the band gaps. We found that, although TbO is stable in a ferromagnetic state, it is stable in RS phase at ambient condition. Both LSDA and PBE-GGA calculations revealed that the three structures are metallic. However, using the mBJ calculation, it is clear that RS and CsCl phases of TbO compound are metallic, while ZB phase is found to be an insulator in the spin-up case and a semiconductor in the spin-down case at ambient pressure.     

Computational investigations of the band structure and thermodynamic properties of calcium-doped BaS using the FP-LAPW approach

In this work, the full-potential linearized augmented plane wave (FP-LAPW) method was used to calculate the structural, electronic, thermal and thermodynamic properties of BaS and CaS compounds and their ternary mixtures, Ba_1?xCa_xS. The local-density approximation (LDA), the Wu-Cohen generalized gradient approximation (WC-GGA) and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) were used as the exchange-correlation potential. Moreover, the modified Becke–Johnson approximation was also used for the band structure calculations. We examined the composition effect on the lattice constants, bulk modulus and band gap. The microscopic origins of the band gap bowing were characterized in detail using the approach of Zunger and colleagues. Pressure and temperature effects on the lattice parameter, heat capacity, Debye temperature, Grüneisen parameter, and thermal expansion coefficient were predicted using the quasi-harmonic Debye model. The thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ?H_m, and the phase diagram. It was shown that these alloys are stable at high temperature.     

First-principle calculations of structural,electronic, optical,elastic and thermal properties of $$\hbox {MgXAs}_{2}$$ ($$\hbox {X}=\hbox {Si}, \hbox {Ge}$$X=Si,Ge) compounds

First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite \(\hbox {MgXAs}_{2}\) (\(\hbox {X}=\hbox {Si}, \hbox {Ge}\)) have been performed within the density functional theory (DFT) using the full-potential linearized augmented plane wave (FP-LAPW) method. The obtained equilibrium structural parameters are in good agreement with the available experimental data and theoretical results. The calculated band structures reveal a direct energy band gap for the interested compounds. The predicted band gaps using the modified Becke–Johnson (mBJ) exchange approximation are in fairly good agreement with the experimental data. The optical constants such as the dielectric function, refractive index, and the extinction coefficient are calculated and analysed. The independent elastic parameters namely, \(C_{11}\), \(C_{12}\), \(C_{13}\), \(C_{33}\), \(C_{44}\) and \(C_{66 }\) are evaluated. The effects of temperature and pressure on some macroscopic properties of \(\hbox {MgSiAs}_{2}\) and \(\hbox {MgGeAs}_{2}\) are predicted using the quasiharmonic Debye model in which the lattice vibrations are taken into account.     

FP-LMTO calculations of elastic and electronic properties of the filled skutterudite CeRu4P12

First-principles calculations have been used to investigate the structural, electronic and elastic properties of the filled skutterudite CeRu₄P₁₂, using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange-correlation energy is described in the local spin density approximation (LSDA) using the Perdew–Wang parameterization. The results of the electronic properties show that this compound is an indirect band gap material. A special interest has been made to the determination of the elastic constants since there have been no available experimental and theoretical data. The energy band gaps and their volume and pressure dependence are investigated. Our results of the ground-state electronic properties are found to agree with experimental results.