The post-perovskite phase has implications for the D′′ layer, which influences the convective mixing in the mantle responsible for plate tectonics.
The crystal system of post-perovskite is orthorhombic, its space group is Cmcm, and its structure is a stacked SiO6-octahedral sheet along the b axis.
Post-perovskite phase is stable above 120 GPa at 2500 K, and exhibits a positive Clapeyron slope such that the transformation pressure increases with temperature.
Such information can be used, for example, to: For these reasons the finding of the MgSiO3-post-perovskite phase transition is considered by many geophysicists to be the most important discovery in deep Earth science in several decades, and was only made possible by the concerted efforts of mineral physics scientists around the world as they sought to increase the range and quality of LHDAC experiments and as ab initio calculations attained predictive power.
The phase transition pressure (characterized by a two-phase loop in this system), was initially thought to decrease as the FeO content increases, but some recent experiments suggest the opposite.
The influence of variable chemistry present in the Earth's lowermost mantle upon the post-perovskite phase transition raises the issue of both thermal and chemical modulation of its possible appearance (along with any associated discontinuities) in the D" layer.
In laser-heated experiments at such high pressures (over 1 million atmospheres), the samples are necessarily small and numerous approximations (e.g., gray body) are required to obtain estimates of the temperature.