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Abstract: Density functional theory pseudo-potential plane-wave calculations are performed in order to predict the structural, elastic and thermodynamic properties of the newly discovered tetragonal intermetallic SrPd2Ge2. The computed equilibrium lattice constants and the internal parameter are in good agreement with the experimental findings. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contraction along the axis is higher than along the axis. The single-crystal elastic constants and related properties are calculated using the static finite strain technique. We predicted the bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio for ideal polycrystalline SrPd2Ge2 aggregates, using the Voigt–Reuss–Hill approximations. We estimated the Debye temperature and minimum thermal conductivity of SrPd2Ge2 from the average sound velocity. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the primitive cell volume, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature are investigated. This is the first quantitative theoretical prediction of the elastic and thermodynamic properties of the SrPd2Ge2 compound, and it still awaits experimental confirmation. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic, optical and thermodynamic properties of the cubic perovskite-type hydride KMgH3 have been investigated using pseudo-potential plane-wave method based on the density functional theory. Computed equilibrium lattice constant agrees well with the available experimental and theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A linear pressure dependence of the elastic stiffnesses is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation for KMgH3 polycrystalline aggregate. The analysis of the site-projected l-decomposed density of states and charge density shows that the bonding is predominantly of ionic nature. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature effect on the lattice constant, bulk modulus, heat capacity and Debye temperature is calculated. [Copyright &y& Elsevier]

Abstract: The structural, electronic, optical and thermodynamic properties of Sr x Ca1−x O, Ba x Sr1−x O and Ba x Ca1−x O ternary alloys in NaCl phase were studied using pseudo-potential plane-wave method within the density functional theory. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, Debye temperatures, mixing entropies and heat capacities on the composition x were analyzed for x =0, 0.25, 0.50, 0.75 and 1. The lattice constant for Sr x Ca1−x O and Ba x Sr1−x O exhibits a marginal deviation from the Vegard''s law, while the Ba x Ca1−x O lattice constant exhibits an appreciable upward bowing. A strong deviation of the bulk modulus from linear concentration dependence was observed for the three alloys. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic, optical and thermodynamic properties of the perovskite chloride CsCdCl3 were investigated using the pseudo-potential plane wave (PP-PW) within the Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA). The computed lattice parameter agrees well with experimental and previous theoretical works. Based on the elastic constants and their related parameters, the crystal rigidity and mechanical stability have been discussed. Energy band structure shows that the investigated material is indirect energy band gap semiconductor. The static dielectric constant and static refractive index are indeed, proportional to the fundamental indirect band gap. The thermal effect on the lattice parameter, bulk modulus, volume expansion coefficient, Grüneisen parameter, heat capacities and Debye temperature were predicted using the quasi-harmonic Debye model. To the best of the authors’ knowledge, most of the studied properties are reported for the first time. [Copyright &y& Elsevier]

The quaternary iridium based hydrides NaAeIrH 6 (Ae = Ca, Ba and Sr) are promising candidates as hydrogen storage materials. We have studied the structural, elastic, electronic, optical and thermodynamic properties of NaAeIrH 6 (Ae = Ca, Ba and Sr) within the generalized gradient approximation, the local density approximation (LDA) and mBj in the frame of density functional perturbation theory. These alloys have a large indirect Γ–X band gap. The thermodynamic functions were computed using the phonon density of states. The origin of the possible transitions from valence band to conduction band was illustrated. By using the complex dielectric function, the optical properties such as absorption, reflectivity, loss function, refractive index and optical conductivity have been obtained. [ABSTRACT FROM AUTHOR]

Abstract: Results of ab initio calculations of the lattice parameter, elastic constants and some thermodynamic parameters in a wide range of pressures and temperatures are reported for the ZnSc2S4 and CdSc2S4 cubic spinels. The calculated equilibrium lattice parameters are compared with available experimental data. Elastic constants and some related properties for single-crystal and polycrystalline have been calculated at zero pressure and zero temperature using the analysis of changes in calculated stresses resulting from changes in strain. Evolution of the elastic constant with pressure and temperature is predicted. From the ab initio calculated total energy versus volume and using the quasi-harmonic Debye model, in which the phononic effects are taken into account, the evolution of some thermodynamic parameters with temperature and pressure is computed. This is the first quantitative theoretical prediction of the reported properties and it still awaits experimental confirmation. [Copyright &y& Elsevier]

• Some Physical properties for BeO 1−x A x alloys are investigated. • The calculated ground states properties for BeA compounds compare well with the available data. • Alloying BeO and BeX change the nature of band gap compared to the parent compounds. • The optical and the thermodynamic properties for are investigated for the first time. Special quasi-random structure (SQS) was used to investigate the structural, electronic, and optical characteristics of the binary and ternary beryllium chalcogenide alloys. The computations were performed using the pseudopotential technique. The GGA-WC scheme was applied to study the structural and optical features of these present alloys, while the HSE06 hybrid functional was used to correct the underestimation of the electronic band structure. The optimized lattice constants and bulk modulus demonstrate a non-linear tendency with increasing x concentration. The phase transition may occur for all ternary alloys at x = 0.5 with the orthorhombic assumed crystal system. The ternary alloys of BeO 1− x A x (A = S, Se) at 0.5 ⩽ x ⩽ 1 have an indirect band gap, while BeO 1− x Te x 0.5 ⩽ x ⩽ 1 manifest a metallic demeanor using HSE06 formalism. The optical spectra were computed and discussed in detail. Furthermore, the thermodynamic stability of the studied compounds was examined using the miscibility critical temperature. [ABSTRACT FROM AUTHOR]