Sakai Takeshi, Dekura Haruhiko, Hirao Naohisa
Geodynamics Research Center, Ehime University, Matsuyama 790-8577, Japan.
Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan.
Sci Rep. 2016 Mar 7;6:22652. doi: 10.1038/srep22652.
The MgSiO3 post-perovskite phase is the most abundant silicate phase in a super-Earth's mantle, although it only exists within the Earth's lowermost mantle. In this study, we established the thermal equation of state (EoS) of the MgSiO3 post-perovskite phase, which were determined by using both laser-heated diamond anvil cell and density-functional theoretical techniques, within a multi-megabar pressure range, corresponding to the conditions of a super-Earth's mantle. The Keane and AP2 EoS models were adopted for the first time to extract meaningful physical properties. The experimentally determined Grüneisen parameter, which is one of the thermal EoS parameters, and its volume dependence were found to be consistent with their theoretically obtained values. This reduced the previously reported discrepancy observed between experiment and theory. Both the experimental and theoretical EoS were also found to be in very good agreement for volumes at pressures and temperatures of up to 300 GPa and 5000 K, respectively. Our newly developed EoS should be applicable to a super-Earth's mantle, as well as the Earth's core-mantle boundary region.
MgSiO₃ 后钙钛矿相是超级地球地幔中最丰富的硅酸盐相，尽管它仅存在于地球最底层的地幔中。在本研究中，我们建立了MgSiO₃ 后钙钛矿相的热状态方程（EoS），该方程是通过使用激光加热金刚石对顶砧池和密度泛函理论技术，在对应于超级地球地幔条件的多兆巴压力范围内确定的。首次采用基恩（Keane）和AP2状态方程模型来提取有意义的物理性质。实验测定的格林爱森参数（Grüneisen parameter）是热状态方程参数之一，发现其与理论值一致，这减少了先前报道的实验与理论之间的差异。实验和理论状态方程在压力高达300 GPa、温度高达5000 K时的体积方面也被发现非常吻合。我们新开发的状态方程应该适用于超级地球的地幔以及地球的核幔边界区域。
