postperovskite

Postperovskite is a crystal structure found in magnesium iron silicate alloys at extremely high pressures and temperatures. It is the high-pressure phase of the mineral perovskite, which is thought to be abundant in the Earth's lower mantle. The transition from perovskite to postperovskite occurs at pressures above approximately 220 GPa and temperatures above 2500 K. This transition is of significant interest to geophysicists because it is believed to mark the boundary between the Earth's lower mantle and the core-mantle boundary.

The postperovskite structure is characterized by layers of (Mg,Fe)O6 octahedra that are distorted and share corners. This arrangement differs from the more symmetric perovskite structure. The discovery of postperovskite, first predicted theoretically and later confirmed by experimental studies, provided a potential explanation for observed seismic discontinuities at the base of the lower mantle. Anomalies in seismic wave velocities observed near the core-mantle boundary are consistent with the presence of the postperovskite phase. Understanding the properties of postperovskite, such as its strength, conductivity, and chemical behavior, is crucial for modeling the dynamics of the deep Earth and the processes that occur at the core-mantle boundary.