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

Abstract The structural, electronic and elastic properties of anti-fluorite Li 2 X (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 Li 2 S and Li 2 Te 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 ( C ij ). Meanwhile, the sound velocity and Debye temperature ( θ D ) are also predicted.