中子衍射
多面体
八面体
价(化学)
钙钛矿(结构)
材料科学
压缩性
外推法
结晶学
衍射
热力学
晶体结构
化学
几何学
物理
数学分析
数学
有机化学
光学
作者
C. David Martin,Ronald I. Smith,William G. Marshall,John B. Parise
出处
期刊:American Mineralogist
[Mineralogical Society of America]
日期:2007-11-01
卷期号:92 (11-12): 1912-1918
被引量:22
摘要
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 Cmc21 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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