First principles study of electronic, elastic and lattice dynamical properties of Mg₂X (X= Si, Ge and Sn) compounds

Abstract

First principles pseudopotential method based on density functional theory is used to investigate the structural, electronic, elastic and phonon properties of Mg₂X (X=Si, Ge, Sn) compounds at ambient pressure in antifluorite (anti-CaF₂-type) structure. The calculated lattice parameters, static bulk modulus, its first order pressure derivatives and the elastic constants are compared with available experimental and other theoretical results. All the compounds have shown very small indirect band gap. The linear response method is applied to determine the phonon dispersion relations and phonon density of states. The phonon frequencies of these compounds are compared with Raman frequency to reveal small LO-TO splitting at zone center.