Mg2Si Silicide under Pressure: First-Principles Evolution Search Results

The search for optimal Mg2Si silicide structures has been performed using the software suite implementing the evolution algorithms on the basis of density functional theory (DFT). It has been shown that the well-known hexagonal structure of P6(3)/mmc symmetry is converted under the pressure P similar to 34 GPa into a monoclinic structure of C2/m symmetry, which is stable up to the pressures P < 76 GPa. This structure is replaced by the orthorhombic Pmmm structure, which is retained up to the pressures P similar to 235 GPa and further gives way to a monoclinic structure of P2/m symmetry. It is demonstrated how the structural transitions P6(3)/mmc -> C2/m -> Pmmm -> P2/m occur under pressure at the atomic level. The structural phase diagram of Mg2Si silicide was plotted within a pressure range of 0-240 GPa.