期刊
AMERICAN MINERALOGIST
卷 92, 期 11-12, 页码 1912-1918出版社
MINERALOGICAL SOC AMER
DOI: 10.2138/am.2007.2585
关键词
post-perovskite; high pressure; structure; neutron diffraction; Rietveld refinement; bond valence; D layer; CaIrO3
The structure of CaIrO3 (Cmcm) has been refined at high pressure and at low temperature using time-of-flight neutron powder diffraction data. Evidence supporting deviation from space group Cmcm to Cmc2(l) is inconclusive. As CaIrO3 (Cmcm) unit-cell volume changes, refinements indicate deformation of cation-centered coordination polyhedra, rather than tilting. Structure models demonstrate Ca2+-centered polyhedra are an order of magnitude more compressible than Ir4+-centered octahedra. Bond valence sums show significant chemical strain (over-bonding) of calcium and oxygen at ambient conditions. Implications for structure change in MgSiO3 post-perovskite are discussed and a method for predicting the Clapeyron slope between perovskite and post-perovskite phases is proposed based on extrapolation of the volume-ratio between cation-centered polyhedra.
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