Study on electronic structures and mechanical properties of new predicted orthorhombic Mg2SiO4 under high pressure

In this work, a new orthorhombic Mg2SiO4 had been predicted by ab-MD and DFT methods. Stability criterion test proved the new phase was possibly and really existing under high pressure. In new predicted phase, besides covalent interaction between Si-3p (outer shell electrons of Si) and O-2p, covalent interaction between Si-2p electrons (inner shell electrons of Si) and O-2s was observed too. One Si and six nearest O atoms formed six Si–O covalent bonds, and built up an uncommon Si–O octahedron. Studies of mechanical properties showed that Mg2SiO4 has excellent stress tolerance. However, shear resistant of Mg2SiO4 was less ideal. Under the condition of continuous pressure, compressional and shear wave velocities increased with pressure discontinuously obviously.