Étude des propriétés structurales, élastiques, électroniques, optiques et thermodynamiques des composés CaSrTt (Tt = Si, Ge, Sn et Pb)

Abstract

We present an ab initio study of structural, elastic, thermodynamic, electronic and optic properties of CaSrTt (Tt=Si, Ge, Sn and Pb) compounds. In order to describe the properties of these materials rather well, the calculations were based on the DFT theory with generalized gradient approximation (GGA). In particular, the calculated lattice constants are in good agreement with experiments with a deviation less than 0.67 %, 2.74 % and 1.7 % for a, b and c respectively. For the equilibrium volume, the deviation does not exceed 4.7 %. Single crystal elastic stiffness’s (Cij) were calculated and the polycrystalline elastic moduli (B and G) were estimated according to Voigt, Reuss and Hill's approximations. The electronic band structure calculations suggest that these compounds are semiconductors, in agreement with literature data on their Ae2Tt analogues. Thermodynamic properties were calculated using GIBBS program which is based on E-V data as the only input parameters. The effect of temperature at various pressure values on the bulk modulus, heat capacities, Debye temperature and coefficient of thermal expansion α was discussed. The variation of various optical parameters such as: the dielectric function, the optical absorption, the refractive index, the extinction coefficient, the optical loss function and the reflectivity at 0GPa, for our compounds, have been studied.