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Hidden Oceans? Unraveling the Structure of Hydrous Defects in the Earth’s Deep Interior
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-07-21 00:00:00 , DOI: 10.1021/jacs.7b05432 Helen Grüninger 1 , Katherine Armstrong 1 , Dominik Greim 1 , Tiziana Boffa-Ballaran 1 , Daniel J. Frost 1 , Jürgen Senker 1
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-07-21 00:00:00 , DOI: 10.1021/jacs.7b05432 Helen Grüninger 1 , Katherine Armstrong 1 , Dominik Greim 1 , Tiziana Boffa-Ballaran 1 , Daniel J. Frost 1 , Jürgen Senker 1
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High-pressure silicates making up the main proportion of the earth’s interior can incorporate a significant amount of water in the form of OH defects. Generally, they are charge balanced by removing low-valent cations such as Mg2+. By combining high-resolution multidimensional single- and double-quantum 1H solid-state NMR spectroscopy with density functional theory calculations, we show that, for ringwoodite (γ-Mg2SiO4), additionally, Si4+ vacancies are formed, even at a water content as low as 0.1 wt %. They are charge balanced by either four protons or one Mg2+ and two protons. Surprisingly, also a significant proportion of coupled Mg and Si vacancies are present. Furthermore, all defect types feature a pronounced orientational disorder of the OH groups, which results in a significant range of OH···O bond distributions. As such, we are able to present unique insight into the defect chemistry of ringwoodite’s spinel structure, which not only accounts for a potentially large fraction of the earth’s entire water budget, but will also control transport properties in the mantle. We expect that our results will even impact other hydrous spinel-type materials, helping to understand properties such as ion conduction and heterogeneous catalysis.
中文翻译：
隐藏的海洋？揭示地球深层内部的含水缺陷的结构
构成地球内部主要部分的高压硅酸盐可能会以OH缺陷的形式掺入大量水。通常，它们通过去除低价阳离子（例如Mg 2+）而达到电荷平衡。通过组合高分辨率多维单和双量子1与密度泛函理论计算h固态NMR谱，我们表明，对于林伍德（γ-Mg系2的SiO 4），另外，硅4+空缺形成，即使含水量低至0.1 wt％。它们通过四个质子或一个Mg 2+进行电荷平衡和两个质子 出人意料的是，还存在很大比例的Mg和Si耦合空位。此外，所有缺陷类型均具有明显的OH基团取向紊乱，从而导致很大范围的OH··O键分布。因此，我们能够对菱锰矿的尖晶石结构的缺陷化学性质提供独特的见解，这种缺陷化学不仅占地球整个水预算的很大一部分，而且还将控制地幔的运输特性。我们希望我们的结果甚至会影响其他含水尖晶石型材料，有助于理解诸如离子传导和非均相催化等性质。
更新日期：2017-07-22
中文翻译：
隐藏的海洋？揭示地球深层内部的含水缺陷的结构
构成地球内部主要部分的高压硅酸盐可能会以OH缺陷的形式掺入大量水。通常，它们通过去除低价阳离子（例如Mg 2+）而达到电荷平衡。通过组合高分辨率多维单和双量子1与密度泛函理论计算h固态NMR谱，我们表明，对于林伍德（γ-Mg系2的SiO 4），另外，硅4+空缺形成，即使含水量低至0.1 wt％。它们通过四个质子或一个Mg 2+进行电荷平衡和两个质子 出人意料的是，还存在很大比例的Mg和Si耦合空位。此外，所有缺陷类型均具有明显的OH基团取向紊乱，从而导致很大范围的OH··O键分布。因此，我们能够对菱锰矿的尖晶石结构的缺陷化学性质提供独特的见解，这种缺陷化学不仅占地球整个水预算的很大一部分，而且还将控制地幔的运输特性。我们希望我们的结果甚至会影响其他含水尖晶石型材料，有助于理解诸如离子传导和非均相催化等性质。
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