Post-Perovskite: The Last Mantle Phase Transition? an Ab Initio Study on Fe-Bearing MgSiO3

Mineral composition, phases, and their relevant properties under the Earth's lower mantle conditions are of fundamental importance for geodynamic modeling and interpreting seismic observation. Good examples include the discovery of the post-perovskite phase of MgSiO3, and potentially the recently reported hexagonal phase (H phase) for (Fe,Mg)SiO3. Fe incorporation will distort the crystal lattice of MgSiO3, because of the different ionic radius of iron relative to magnesium and silicon; the extra degree of freedom—spin state, also plays a crucial role in stabilizing certain structures. In this presentation, we report our exploration on possible new phases based on ab initio methods. The results will be compared with experiments and discussed in detail.