Small shear modulus of cubic CaSiO3 perovskite
Small shear modulus of cubic CaSiO3 perovskite
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DOI：
10.1002/2015gl063446
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发表时间：
2015-04-28
影响因子：
5.2
通讯作者：
Tsuchiya, Taku
中科院分区：
文献类型：
--
作者：
Kawai, Kenji;Tsuchiya, Taku
钙钛矿（CaPv）被认为是地球下地幔（LM）中最丰富的矿物之一。此外，先前的静态计算和平均场理论表明，它具有比桥菱铁矿（MgPv）大得多的剪切模量。在正确的条件下，采用密度泛函恒温第一性原理分子动力学方法，重新研究了立方CaPv的弹性。我们的新结果清楚地表明，立方CaPv具有与含铁MgPv相当的体积和略小的剪切模量。这是因为本研究使用的超级单体的边界条件允许SiO6八面体在应变下的旋转声子运动，这主要影响C-11和C-44的减少。由弹性模量确定的声波速度表明，在LM中，立方CaPv比含铁MgPv和初步参考地球模型具有更慢的速度和更大的密度。这表明，如果存在富含capv的物质，它可能积聚在最底部的LM中，并产生地震低速异常。
Ca-perovskite (CaPv) is considered to be one of the most abundant minerals in the Earth's lower mantle (LM). Furthermore, previous static calculations and mean-field theory suggest that it has a much larger shear modulus than bridgmanite (MgPv). In this study, the elasticity of cubic CaPv was reinvestigated using the density functional constant-temperature first principles molecular dynamics method under the correct conditions to simulate its elasticity. Our new results clearly demonstrate that cubic CaPv has comparable bulk and slightly smaller shear moduli than Fe-bearing MgPv. This is because the boundary condition for the supercell used in this study allows for the rotational phonon motion of SiO6 octahedra under strain, which predominantly affects the decrease in C-11 and C-44. Acoustic wave velocities determined from the elastic moduli indicate that cubic CaPv has slower velocities and larger densities than Fe-bearing MgPv and preliminary reference Earth model in the LM. This suggests that if CaPv-rich material exists, it can accumulate in the lowermost LM and produce a seismically low-velocity anomaly.