Ab initio search for low-pressure analogs of MgSiO₃ post-perovskite at ultrahigh pressures

MgSiO₃ post-perovskite (Mg-PPV) is the final form of this silicate in the Earth’s mantle. However, the fate of Mg-PPV in the mantle of terrestrial exoplanets, where pressures and temperatures are much higher than those on Earth, is still an open question. Our previous ab initio studies revealed a complex series of phase transitions involving dissociation (MgSiO₃ → Mg₂SiO₄ + MgSi₂O₅ → Mg₂SiO₄ + SiO₂ → MgO + SiO₂) and recombination (MgO + MgSiO₃ → Mg₂SiO₄ or SiO₂ + MgSiO₃ → MgSi₂O₅) reactions among silicates and elementary oxides [1,2]. These transitions also depend on the chemical compositions of planetary mantles and occur at very high pressure (above ~0.5 TPa), which makes experimental validation rather difficult. To facilitate experimental validation, it is highly desirable to conduct experiments in low-pressure analogs of Mg-PPV. Here, we search for these low-pressure analogs using ab initio calculations.


[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] K. Umemoto, R. M. Wentzcovitch, S. Q. Wu, M. Ji, C. Z. Wang, and K. M. Ho, Earth Planet. Sci. Lett. 478, 40 (2017).