A first-principles study of the structural, elastic, electronic and phonon properties of LiMgP and LiMgAs in the α, β and γ phases

We have studied the structural, elastic, electronic and phonon properties of LiMgP and LiMgAs in the α, β and γ phases by employing the plane wave pseudopotential method based on density functional theory, within the local density approximation. Lattice parameters, bulk modulus and its pressure derivative, and second order elastic constants were found in good agreement with the literature data. We found that the γ phase of these compounds are in metallic nature as opposed to α and β phases. A linear-response approach to density functional theory was used to derive the phonon dispersion and the phonon density of states. The calculated zone-center optical phonon modes for these materials were compared with available experimental and theoretical results. Atomic displacement patterns for LiMgP in α phase at Γ and X symmetry points were presented.