PRESSURE-RELATED PHASE STABILITY OF MgSiO3 and(Mg0.75, Feo.25) SiO3 AT LOWER MANTLE CONDITION

摘要

Relative stability of different phases for MgSiO3 and (Mgo75, Fe0.25) SiO3 within0-110 GPa are investigated using first-principles method. For MgSiO3, the computedequation of state for orthorhombic phase of Pbnm space group agrees well with experi-mental results. The relative stability reduces from observed Pbnm orthorhombic phase tointermediated tetragonal P4mbm phase, and then to hypothetical cubic Pm3m phase.For (Mg075, Feo.25) SiO3, the same sequence of relative phase stability is observed.Thus, the low-symmetric orthorhombic MgSiO3 should be favored in the lower mantlecondition, while adding Fe into MgSiO3 will make it less stable at the same depth.