Ab initio structural and electronic band-structure study of MgSe

We present a careful and detailed ab initio study of the crystal structure and electronic band structure of different crystalline phases of MgSe. Calculations were performed using the fullpotential linear augmented plane wave method. To determine the crystal phase of the ground state of MgSe, we computed the total energy as a function of volume for the rock-salt, zincblende, wurtzite, and NiAs phases. From the optimized volume, and by using the Birch-Murnaghan equation of state the lattice parameters a(0) (c(0)), the bulk moduli, and its first pressure derivative (B-0 and B-0') for the different phases of MgSe were found. In our calculations, we have used the local density approach for the exchange-correlation part of the total energy. It was determined that in this approach the sequence of phase transformations under pressure is rock-salt-NiAs-wurzite-zinc-blende. However, we also found that under ambient conditions, the different studied phases for MgSe are energetically available. Using the modified Becke-Johnson exchange correlation potential, the calculated values of the bandgap were improved, and the results are comparable to existing experimental values for the zinc-blende phase. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim