Post-perovskite Phase: Findings, Structure and Property
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Experimental study by (1994) on natural garnets in a laser-heated diamond-anvil under 30 GPa showed transformation of this phase to a new mineral having a perovskite like structure. Subsequently mineral physicists observed that all essential mantle minerals transformed to an assemblage comprising perovskite or rock salt like structure. While studying pyrolitic assemblage under lower mantle conditions, Hirose et al. observed that between 110 and 120 GPa a new phase appeared. It had a structure with Cmcm space group and was isostructural with UFeS3. It had a layered structure made up of two types of layers. One layer had a two-dimensional network of SiO6 octahedra, connected by edge or corner sharing along the direction of a and c axis. The other layer is formed by Mg cation.
The P-T condition or depth of transformation of perovskite to post-perovskite structure coincides with the D″ layer of the earth. As this layer shows seismic anisotropy, it has been postulated that materials with post-perovskite structure may have lattice preferred orientation (LOP). This paper also describes deformation experiments related to development of LOP in the material with post-perovskite structures.
KeywordsPerovskite Phase Lower Mantle Seismic Anisotropy Lattice Prefer Orientation Photon Factory
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