Ab initio anharmonic thermodynamic properties of cubic CaSiO3 perovskite
Ab initio anharmonic thermodynamic properties of cubic CaSiO3 perovskite
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DOI：
10.1103/physrevb.103.104108
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发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Zhen Zhang;R. Wentzcovitch
中科院分区：
文献类型：
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作者：
Zhen Zhang;R. Wentzcovitch
本文研究了立方钙钛矿CaPv在地球下地幔压力和温度范围内的热力学性质。我们利用声子准粒子方法计算了整个布里渊区的非简谐声子色散，该方法表征了声子频率的本征温度依赖关系，并且原则上捕捉到了完全的非谐性。这种依赖温度的声子色散被用来在声子气体模型的框架内计算热力学极限($N\right tarrow\infty$)中的自由能。精确的自由能计算使我们能够研究立方CaPv的热力学性质和热态方程，其中展示了非简谐效应。本方法为探索高温高压下强非简谐材料的相界、热力学和热弹性性质提供了重要的理论方法。
We present an $\textit{ab initio}$ study of the thermodynamic properties of cubic CaSiO$_3$ perovskite (CaPv) over the pressure and temperature range of the Earth's lower mantle. We compute the anharmonic phonon dispersions throughout the Brillouin zone by utilizing the phonon quasiparticle approach, which characterizes the intrinsic temperature dependence of phonon frequencies and, in principle, captures full anharmonicity. Such temperature-dependent phonon dispersions are used to calculate $\textit{ab initio}$ free energy in the thermodynamic limit ($N \rightarrow \infty$) within the framework of the phonon gas model. Accurate free energy calculations enable us to investigate cubic CaPv's thermodynamic properties and thermal equation of state, where anharmonic effects are demonstrated. The present methodology provides an important theoretical approach for exploring phase boundaries, thermodynamic, and thermoelastic properties of strongly anharmonic materials at high pressures and temperatures.