Structural and elastic anisotropy of crystals at high pressures and temperatures from quantum mechanical methods: The case of Mg2SiO4 forsterite,The Journal of Chemical Physics

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Structural and elastic anisotropy of crystals at high pressures and temperatures from quantum mechanical methods: The case of Mg2SiO4 forsterite
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2015-05-28 14:51:41 , DOI: 10.1063/1.4921781
A. Erba ₁ , J. Maul _{1,

2} , M. De La Pierre ₃ , R. Dovesi ₁

Affiliation

We report accurate ab initio theoretical predictions of the elastic, seismic, and structural anisotropy of the orthorhombic Mg₂SiO₄ forsterite crystal at high pressures (up to 20 GPa) and temperatures (up to its melting point, 2163 K), which constitute earth’s upper mantle conditions. Single-crystal elastic stiffness constants are evaluated up to 20 GPa and their first- and second-order pressure derivatives reported. Christoffel’s equation is solved at several pressures: directional seismic wave velocities and related properties (azimuthal and polarization seismic anisotropies) discussed. Thermal structural and average elastic properties, as computed within the quasi-harmonic approximation of the lattice potential, are predicted at high pressures and temperatures: directional thermal expansion coefficients, first- and second-order pressure derivatives of the isothermal bulk modulus, and P-V-T equation-of-state. The effect on computed properties of five different functionals, belonging to three different classes of approximations, of the density functional theory is explicitly investigated.

中文翻译：

量子力学方法在高压和高温下晶体的结构和弹性各向异性：以镁镁橄榄石为例

我们报告了正交晶体Mg ₂ SiO ₄的弹性，地震和结构各向异性的从头开始的准确理论预测于高温（高达20 GPa）和高温（高达2163 K熔点）的镁橄榄石晶体，构成了地球的上地幔条件。对单晶的弹性刚度常数进行了高达20 GPa的评估，并报告了它们的一阶和二阶压力导数。Christoffel方程是在几种压力下求解的：讨论了定向地震波的速度和相关特性（方位角和极化地震各向异性）。热结构和平均弹性性质，因为晶格潜在的准谐波近似内计算，是在高压和高温下的预测：定向的热膨胀系数，等温体积弹性模量的一阶和二阶压力的衍生物，和P - V -T状态方程。明确研究了密度泛函理论的五个不同泛函（分别属于三种不同的近似类别）对计算属性的影响。

更新日期：2015-05-31

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