Phase stability and shear softening in CaSiO3 perovskite at high pressure
Phase stability and shear softening in CaSiO3 perovskite at high pressure
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DOI：
10.1103/physrevb.75.024108
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发表时间：
2007-01
影响因子：
3.7
通讯作者：
L. Stixrude;C. Lithgow‐Bertelloni;B. Kiefer;P. Fumagalli
中科院分区：
文献类型：
--
作者：
L. Stixrude;C. Lithgow‐Bertelloni;B. Kiefer;P. Fumagalli
140 GPa。在100 GPa下，四元结构的c/a比为1.018，并且随着压缩而增加，四元结构和立方结构之间的静态焓差也是如此。在静态条件下的四方相的弹性常数与立方相的弹性常数有很大的不同，在100 GPa下的Voigt-Reuss-Hill剪切模量小29%。计算是基于密度泛函理论的局部密度和广义梯度近似。相图和高温弹性常数计算使用平均场理论与参数的朗道潜在的结构约束密度泛函理论计算确定。我们提出了一个简单的计划，系统地搜索所有的钙钛矿结构的基态可从八面体旋转的背景下的dopypreserving松弛，这证实了tetrahydroxide I4/mcm的密度泛函理论的基态。我们认为，实验的X-射线衍射图案可以解释I4/MCM相通过考虑单轴压缩下的择优取向的发展。
140 GPa. The c/a ratio of the tetragonal structure is 1.018 at 100 GPa and increases on compression, as does the static enthalpy difference between tetragonal and cubic structures. The elastic constants of the tetragonal phase at static conditions differ substantially from those of the cubic phase with the Voigt-Reuss-Hill shear modulus 29% less at 100 GPa. Computations are based on density functional theory in the local density and generalized gradient approximations. The phase diagram and high temperature elastic constants are computed using a mean field theory with parameters of the Landau potential determined via structurally constrained density functional theory calculations. We present a simple scheme for systematically searching for the ground state over all perovskite structures derivable from octahedral rotations within the context of symmetrypreserving relaxation, which confirms tetragonal I4/mcm as the ground state in density functional theory. We argue that the experimental x-ray diffraction pattern can be explained by the I4/mcm phase by considering the development of preferred orientation under uniaxial compression.