Materials Properties for Modeling Planetary Formation

Umemoto et al. wanted to understand what happens to the structure of MgSi03 at conditions much more extreme than those found in Earth s core-mantle boundary. They used DFT calculations to construct a phase diagram that compared the stability of multiple possible crystal structures of solid MgSi03. All of these calculations dealt with bulk materials. They also considered the possibility that MgSi03 might dissociate into other compounds. These calculations predicted that at pressures of 11 Mbar, MgSi03 dissociates in the following way  

In this reaction, the crystal stmcture of each compound has been noted in the square brackets. An interesting feature of the compounds on the right-hand side is that neither of them is in the crystal structure that is the stable structure at ambient conditions. MgO, for example, prefers the NaCl structure at ambient conditions (i.e., the same crystal structure as everyday table salt). The behavior of Si02 is similar but more complicated this compound goes through several intermediate structures between ambient conditions and the conditions relevant for MgSi03 dissociation. These transformations in the structures of MgO and Si02 allow an important connection to be made between DFT calculations and experiments since these transformations occur at conditions that can be directly probed in laboratory experiments. The transition pressures 

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