First principles study of structural phase stability of wide-gap semiconductors MgTe, MgS and MgSe

The structural stability of different crystallographic phases of three magnesium chalcogenides, MgTe, MgS and MgSe, are investigated from first principles calculations based on density functional theory (DFT) using projector augmented waves (PAW) potentials within both generalized gradient approximation (GGA) and local density approximation (LDA). Five different phases of these compounds, rock-salt (B1), cesium chloride (B2), zinc-blende (B3), wurtzite (B4) and NiAs (B81), are considered in detail. LDA calculations of the ground state structure of all compounds considered are in accordance with previous studies, while calculations with GGA functionals resulted interesting perspectives. Ground state stable phases of MgS and MgSe are found as rock-salt structure, while the NiAs is the ground state of MgTe within the LDA scheme. But GGA calculations show that the ground states of MgTe and MgSe are wurtzite, while the ground state of MgS is same as in LDA calculations. There is also a structural transition observed for MgTe around ∼1.2 GPa pressure from wurtzite to NiAs by GGA calculations. The calculated quantities show that the rock-salt–NiAs and zinc-blende–wurtzite pairs have similar energetics. The calculated structural quantities for all compounds under study in all phases agree well with the available experimental and theoretical values.