Ab initio study of the structural, electronic and elastic properties of anti-fluorite Li2X (X = S and Te) compounds under pressure effect

The structural, electronic and elastic properties of anti-fluorite Li2X (X = S and Te) compounds were investigated by means of density functional theory. The generalized gradient approximation (GGA) within the Perdew-Burke-Ernzerhof (PBE) scheme and the local density approximation (LDA) with the Teter-Pade (TP) parameterization have been used for the exchange-correlation term. Our calculated lattice parameters at equilibrium volume are in good agreement with available experimental data and other theoretical calculations. The electronic band structure calculation reveals that the anti-fluorite Li2S and Li2Te present, at equilibrium, an indirect band gap of 3.388 eV and 2.493 eV respectively. The partial density of states plots reflect the p electronic contribution, through the top of the valence bands, for both systems. Furthermore, elastic properties including bulk modulus, shear modulus, Young's modulus (E) and Poisson's ratio ( v) are deduced from calculated elastic constants (Cu). Meanwhile, the sound velocity and Debye temperature (O-D) are also predicted. (C) 2014 Elsevier B.V. All rights reserved.