First principles calculation of structural phase transformation in Mg2Si at high pressure

First principles calculations of the total energy of Mg2Si as a function of unit cell volume have been carried out for the cubic anti-fluorite (Fm3m) structure, the orthorhombic phase with anti-cotunnite (Pnma) structure and the hexagonal phase with Ni2In-type (P63/mmc) structure on the basis of density functional theory (DFT). All these calculations are performed with the CRYSTAL06 program package. In agreement with experiment, we also obtained the sequence of high-pressure phases for Mg2Si as: anti-fluorite → anti-cotunnite → Ni2In-type. Several structural properties (equilibrium lattice constant, bulk modulus, etc.) of the anti-fluorite structure have been calculated, which are also in agreement with the previous experimental results.