ABSTRACT 3.65 Å-phase (or hydroxide-perovskite), MgSi(OH)6, is a representative of dense hydrous magnesium silicates (DHMS) with maximum water content (up to ∼35 wt.% H2O) and thus is of interest as one of the largest repositories of water among all the known hydrous phases. Sample of 3.65 Å-phase, grown in DIA-type multianvil apparatus, was studied by Raman spectroscopy under pressure up to ∼7 GPa with diamond anvil cell. Interpretation of the Raman spectrum was carried out using lattice-dynamical simulations within ab initio DFT method (CASTEP code). Additionally, OH-stretching bands are analyzed with two phenomenological models: empirical model by Novak and Libowitzky, using correlation between O–O distance and the wavenumber of the OH-stretching band, and theoretical model, using double Morse potentials of hydrogen bond O–H···O. Upon the pressure increase, octahedral and bending δ(ОН) vibrations exhibit linear positive pressure shift, whereas wavenumbers of the ОН-stretching modes show inverse pressure dependence.

中文翻译：

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高压下 3.65 Å 相 MgSi(OH)6 的拉曼研究和谱带分配

摘要 3.65 Å 相（或氢氧化物-钙钛矿）MgSi(OH)6 是具有最大含水量（高达 35 wt.% H2O）的致密含水硅酸镁 (DHMS) 的代表，因此作为一种在所有已知水相中最大的水库。在 DIA 型多砧装置中生长的 3.65 Å 相样品，通过拉曼光谱在高达 ~7 GPa 的压力下使用金刚石砧座进行研究。拉曼光谱的解释是在 ab initio DFT 方法（CASTEP 代码）中使用晶格动力学模拟进行的。此外，使用两种现象学模型分析 OH 拉伸带：Novak 和 Libowitzky 的经验模型，使用 O-O 距离与 OH 拉伸带的波数之间的相关性，以及理论模型，使用氢键 O-的双摩尔斯势H···O.