Compression, thermal expansion, structure, and instability of CaIrO3, the structure model of MgSiO3 post-perovskite
Compression, thermal expansion, structure, and instability of CaIrO3, the structure model of MgSiO3 post-perovskite
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DOI：
10.2138/am.2007.2473
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发表时间：
2007-07-01
影响因子：
3.1
通讯作者：
Parise, John B.
中科院分区：
文献类型：
--
作者：
Martin, C. David;Chapman, Karena W.;Parise, John B.
对压力-温度关系的单色X射线粉末衍射数据进行分析，得到了体弹性系数[K-T=180.2(28)Gpa]和热膨胀系数[α(0)2.84](34)×10(-5)K-1；α(1)=226.3754(48)×10(-9)K-2]，后钙钛矿型镁硅中心点CaIrO_3的结构模型为正交晶系，晶胞参数最佳，a=3.14147(5)埃，b=9.87515(19)埃，c=7.29711(11)埃，V=226.3754(78)埃(3)。与其他主轴相比，CaIrO_3的c轴具有较小的可压缩性和较大的热膨胀。Rietveld结构的改进揭示了开罗的变化，作为IrO6八面体扭曲的温度函数。CaIrO_3在高温下的解离可能对后钙钛矿结构、地球下地幔和D‘’层具有重要意义。
Analysis of pressure-temperature dependent monochromatic X-ray powder diffraction data yield the bulk modulus [K-T = 180.2(28) GPa] and thermal expansion coefficients [alpha(0) 2.84](34) x 10(-5) K-1; alpha(1) = 3.37(48) x 10(-9) K-2] of CaIrO3, the structure model for post-perovskite MgSiO3 center dot CaIrO3 is orthorhombic (Cmcm, space group 63, Z = 4) with best-fit unit-cell parameters, a = 3.14147(5) angstrom, b = 9.87515(19), c = 7.29711(11), and V = 226.3754(78) angstrom(3) at 1 bar and 300 K. The c-axis of CaIrO3 has a small compressibility and a large thermal expansion when compared to the other principal axes. Rietveld structure refinement reveals changes in CaIrO, as a function of temperature in terms of IrO6 octahedra distortion. Dissociation of CaIrO3, at high temperature has possible implications for the post-perovskite MgSiO3 structure, Earth's lower mantle, and D '' layer.