Theoretical prediction of the elastic, electronic and optical properties of the filled tetrahedral semiconductor α-LiMgSb

We have investigated the structural, elastic, electronic and optical properties of the filled tetrahedral semiconductor α-LiMgSb using the pseudo-potential plane-wave approach within the density functional theory. The calculated equilibrium lattice constant is in good agreement with the experimental result. The independent elastic constants and elastic wave velocities are calculated for α-LiMgSb and its zinc-blende analogue AlSb from direct computation of stresses generated by small strains. Numerical estimates of a set of isotropic elastic parameters are performed in framework of the Voigt-Reuss-Hill approximation for the ideal polycrystalline α-LiMgSb aggregates. An analysis of the bonding situation in this compound has been done in terms of the band structure, the site-projected l-decomposed density of states and the electron charge density plots. Calculations of the optical spectra, namely the dielectric function, optical reflectivity, refractive index, extinction coefficient and electron energy loss, are performed for the energy range 0-15 eV. This is the first quantitative theoretical prediction of the elastic, electronic and optical properties of the α-LiMgSb compound that requires experimental confirmation.