The Stability of MgSiO$_{3}$ Perovskite at Lower Mantle Conditions

The stability of MgSiO$_{3}$-perovskite at lower mantle conditions has been a subject of extensive investigation and debate. Shock recovery experiments with the initial sample of (Mg$_{0.92}$, Fe$_{0.08})$SiO$_{3}$ enstatite and MgO+SiO$_{2}$ were conducted up to 120GPa. The analysis of XRD results indicate that there is no possibility for the chemical decomposition from (Mg$_{0.92}$, Fe$_{0.08})$SiO$_{3}$ to oxides SiO$_{2}$ and (Mg$_{0.92}$, Fe$_{0.08})$O under experimental shock pressure. The Gibbs energy and molar volume of all phases in the reaction MgSiO$_{3}$(Pv) = MgO(Pe) + SiO$_{2}$(St) are calculated using both the latest experimental thermodynamic parameters and the first principle molecular dynamic (MD) simulations under lower mantle conditions (1000-3500K and 30-150GPa)., and the results show that perovskite is thermodynamically stable relative to the stishovite and periclase assemblage at lower mantle conditions.