Post‐oxide phases of forsterite and enstatite

Both forsterite (Mg 2 SiO 4 ) and enstatite (MgSiO 3 ) enter a post‐oxide phase characterized by the orthorhombic perovskite structure when subjected to high pressure and temperature in the diamond‐anvil press coupled with laser heating. The lattice parameters for the perovskite phase of MgSiO 3 are a o = 4.790 ± 0.002, b o = 4.943 ± 0.002, and c o = 6.897 ± 0.003 Å with Z = 4. The calculated density of MgSiO 3 (perovskite) is thus 4.083 g/cm³, or 2.8% denser than its isochemical mixed oxides with rocksalt and rutile structures. The density of a mixture of MgSiO 3 (perovskite) plus MgO (periclase) is 1.9% greater than that of the mixed oxides with the forsterite stoichiometry.