Fate of MgSiO3 post-perovskite at multi-Mbar pressures*

The discovery of the post-perovskite (PPV) transition of MgSiO$_{3}$ in 2004 invited a new question: What would be the next phase transition from the PPV phase? The importance of this question has increased, since many terrestrial exoplanets with masses of a few to 10 times Earth's (super-Earth) have been recently discovered. Here we predict the new class of phase transitions of MgSiO$_{3}$ PPV under ultrahigh pressure by first-principles calculations combined with the adaptive genetic algorithm, which is a powerful tool for blind structural searches for systems with the large number of atoms. We discuss implications of these new phase transitions in modeling of interiors of terrestrial exoplanets.