High-pressure phase of brucite stable at Earth's mantle transition zone and lower mantle conditions
High-pressure phase of brucite stable at Earth's mantle transition zone and lower mantle conditions
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DOI：
10.1073/pnas.1611571113
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发表时间：
2016-12-06
影响因子：
11.1
通讯作者：
Mookherjee, Mainak
中科院分区：
文献类型：
--
作者：
Hermann, Andreas;Mookherjee, Mainak
本文采用结构搜索算法和从头计算方法研究了水合矿物水镁石Mg（OH）（2）的高压相图。我们预测，在地幔过渡带和下地幔的冷俯冲板中发现的压力和温度条件下，高压相是稳定的。这一预测意味着水镁石在地球内部的水运输和储存方面可以发挥比迄今为止认为的更重要的作用。预测的高压相，稳定在20和35 GPa之间的计算和高达800 K，具有MgO 6八面体单元排列在锐钛矿-TiO 2结构。我们的研究结果表明，水镁石将从一个层状转化为一个紧凑的三维网络结构，最终分解成方镁石和冰。我们表明，高压阶段具有独特的光谱指纹，应该允许在实验中直接检测。该相位还具有独特的弹性特性，这可能使其在地球深部的直接探测成为可能。
We investigate the high-pressure phase diagram of the hydrous mineral brucite, Mg(OH)(2), using structure search algorithms and ab initio simulations. We predict a high-pressure phase stable at pressure and temperature conditions found in cold subducting slabs in Earth's mantle transition zone and lower mantle. This prediction implies that brucite can play a much more important role in water transport and storage in Earth's interior than hitherto thought. The predicted high-pressure phase, stable in calculations between 20 and 35 GPa and up to 800 K, features MgO6 octahedral units arranged in the anatase-TiO2 structure. Our findings suggest that brucite will transform from a layered to a compact 3D network structure before eventual decomposition into periclase and ice. We show that the high-pressure phase has unique spectroscopic fingerprints that should allow for straightforward detection in experiments. The phase also has distinct elastic properties that might make its direct detection in the deep Earth possible with geophysical methods.