Structure of MgO(MgSiO$_{3})_{n}$ in Earth's Lower Mantle: ab initio calculations

Ruddlesden-Popper (RP) compounds are composed of alternating perovskite-type and rocksalt-type structural elements. MgSiO$_{3}$ and MgO are found as separate phases in Earth's lower mantle. Both structural elements occur also in the hypothetical RP-series MgO(MgSiO$_{3})_{n}$. It is interesting to explore the high pressure-high temperature stability of such RP-structures. Using the augmented plane wave implementation of Density Functional Theory we investigate the structural stability at lower mantle conditions of the member with $n$ = 1 e.g. Mg$_{2}$SiO$_{4}$. The goal of the present calculations is to test the stability of this Ruddlesden-Popper phase relative to $\gamma$-(Mg,Fe)$_{2}$SiO$_{4}$ and the assemblage MgSiO$_{3}$-perovskite + MgO magnesiow\"{u}stite. We will present our results of this study.