First principles vibrational dynamics of magnesium telluride

The lattice dynamics of large-gap semiconductor MgTe compound at various crystallographic phases; rocksalt (B1), zincblende (B3), NiAs (B81) and wurtzite (B4), has been investigated from first principles calculations based on density functional theory (DFT) within plane-wave pseudopotential method and generalized gradient approximation (GGA) of the exchange-correlation functional. The static equation of states of the compound has been studied with Vinet equation of states. The ground state of the compound is a fourfold coordinated wurtzite structure, which is consistent with experiments and recent theoretical calculations. Full phonon dispersion spectra of all related phases of the MgTe have been calculated using density functional perturbation theory within the linear-response approach. In view of the total energy calculations and the obtained vibrational spectra, it can be emphasized that the MgTe polymorphs with tetrahedral coordination (zincblende and wurtzite structures) are of covalent character rather than ionic. The large TO–LO splitting of phonon branches of rocksalt and NiAs phases reflect the high ionicity of these phases.