First-principles studies of ground-state and dynamical properties of MgS, MgSe, and MgTe in the rocksalt, zinc blende, wurtzite, and nickel arsenide phases

An ab initio pseudopotential method is used to investigate the structural and electronic properties of MgS, MgSe, and MgTe in the rocksalt, zinc blende, wurtzite, and nickel arsenide phases. It is found that rocksalt is the most stable phase for MgS and MgSe, while nickel arsenide is the most stable phase for MgTe. Differences in the density of states for the upper valence bands and lower conduction bands between these competing phases are pointed out. The lattice dynamics of these semiconductors has been studied by employing a linear response approach based on the density functional theory. Differences in the phonon spectra and density of states both in the acoustic and optical ranges between the competing phases are investigated. The calculated zone-center phonon modes for the rocksalt and zinc blende phases of MgS are in good agreement with experimental observations.