Keywords:First-principles method, internally consistent LSDA+U, post-perovskite, phase transition
The post-perovskite (PPv) phase transition of MgSiO3 bridgmanite (Br) [1,2,3] occurs in the pressure (P) and temperature (T) conditions corresponding to the Earth's D? layer. Therefore, MgSiO3 PPv is believed to be a key mineral to understanding the seismological properties in this layer. However, to date, it is still a challenging subject to determine the phase transition boundary preciously in the geophysically relevant Fe and Al-bearing compositions. Based on the first-principles methods combined with the internally consistent LSDA+U method and the lattice dynamics approach, the high-P and high-T thermodynamics of the MgSiO3 phases are directly calculated with incorporation of 6.25 mol% of Fe2+, Fe3+Fe3+, Fe3+Al3+, and Al3+Al3+ [4,5]. Using calculated free energies, we determine the PPv phase boundaries for Fe and Al-bearing compositions. Our results show that at 2500 K, the Fe3+Al3+ and Fe3+Fe3+ incorporations span coexisting domains between Br and PPv significantly with lowering the transition pressure, in contrast to the Fe2+- and Al3+Al3+-bearing cases.
 M. Murakami, K. Hirose, K. Kawamura, N. Sata, and Y. Ohishi, Science 304, 855 (2004).
 A. Oganov, and S. Ono, Nature 430, 445 (2004).
 T. Tsuchiya, J. Tsuchiya, K. Umemoto, and R. M. Wentzcovitch, Earth. Planet. Sci. Lett. 224, 241 (2004).
 J. Tsuchiya, and T. Tsuchiya, Proc. Natl. Acad. Sci. USA 105, 19160 (2008).
 A. Metsue, and T. Tsuchiya, Geophys. J. Int. 190, 310 (2012).