[S-IT23] [EE] Structure and Dynamics of Earth and Planetary Mantles

[SIT23-18] Fate of MgSiO₃ post-perovskite in super-Earths

*Koichiro Umemoto¹, Renata Wentzcovitch², Shunqing Wu³, Kai-Ming Ho³, Min Ji³, Cai-Zhuang Wang³ (1.Earth-Life Science Institute, Tokyo Institute of Technology, 2.Columbia Universitity, 3.Iowa State University)

Keywords:MgSiO3 post-perovskite, pressure-induced phase transition, first-principles calculation, terrestrial exoplanets

MgSiO₃ post-perovskite (ppv) is the final form of MgSiO₃ in the Earth. However, what happens in super-Earths in which pressure and temperature are much higher than those of the Earth’s lower mantle? Understanding of fate of MgSiO₃ ppv under ultrahigh pressures is crucial for nature of interiors of super-Earths. Computational studies so far have predicted several pressure-induced dissociations of MgSiO₃ in super-Earths. Recent studies agree that MgSiO₃ ppv undergoes three-stage dissociations involving MgO, SiO₂, Mg₂SiO₄, and MgSi₂O₅ [1,2]. Based on these studies, we reinvestigate the high PT phase diagram of MgO-SiO2 system and we propose a new phase transition in MgO-SiO₂ system in super-Earths. Clapeyron slope of the new transition and thermodynamic quantities calculated for these phases should provide fundamental information for numerical simulation of mantle dynamics in super-Earths.

[1] S. Q. Wu, M. Ji, C. Z. Wang, M. C. Nguyen, X. Zhao, K. Umemoto, R. M. Wentzcovitch, K. M. Ho, J. Phys. Condensed Matter, 26, 035402 (2014).
[2] H. Niu, A. R. Oganov, X. Q. Chen, and D. Li, Sci. Rep. 5, 18347 (2015).