The fate of MgSiO3 post-perovskite under TPa pressures is key information for understanding and modeling interiors of super-Earths-type exoplanets and solar giants' cores. Here, we report a dissociation of MgSiO3 post-perovskite into CsCl-type MgO and P21/c-type MgSi2O5 at ~0.9TPa obtained by first principles calculations. P21/c-type MgSi2O5 should dissociate further into CsCl-type MgO and Fe2P-type SiO2 at ~2.1TPa. The first dissociation should occur in all solar giants and heavy super-Earths, while the second one should occur only in Jupiter and larger exoplanets. Both dissociations are endothermic and have large negative Clapeyron slopes. If the first dissociation should occur in the middle of a silicate mantle, it could promote mantle layering. We provide essential thermodynamic properties of P21/c-type MgSi2O5 for modeling interiors of super-Earths.
Bibliographical noteFunding Information:
We would like to thank Professor D. A. Yuen for fruitful discussions. Calculations have been done using the Quantum-ESPRESSO package ( Giannozzi et al., 2009 ) and VLab software ( da Silveira et al., 2008 ). Research was supported by NSF grants EAR-1047629 . Computations were performed at the Minnesota Supercomputing Institute and at the Laboratory for Computational Science and Engineering at the University of Minnesota.
- 10 solar giants
- First principles
- Pressure-induced phase transition