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

[SIT23-18] 地球型系外惑星内においてMgSiO₃はどうなるか

*梅本 幸一郎¹、Wentzcovitch Renata²、Wu Shunqing³、Ho Kai-Ming³、Ji Min³、Wang Cai-Zhuang³ (1.東京工業大学地球生命研究所、2.コロンビア大学、3.アイオワ州立大学)

キーワード：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).