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.
 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).
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