Unraveling the structure of high-pressure hydrous silicate melts by multi-dimensional NMR spectroscopy and ab intio calculations

本研究的目的是揭示高压下含水（铝）硅酸盐熔体（玻璃）的结构，以了解天然岩浆的行为。主要成就概述如下：多核、多维核磁共振技术的发展。多维核磁共振技术是特别强大的结构工具，因为它们提供了关于原子连接的直接信息。我们已经成功地进行了各种核磁共振测量，包括^1H DQ（双量子）MAS NMR, ^<27>Al- 3Q（三量子）MAS NMR，和^<27>Al-^1H hetkor（异核相关）和3QMAS/ hetkor NMR.2。解决了关于聚合硅酸铝熔体水溶解机理的长期争论。通过上述技术，我们证实了水在聚合硅酸铝熔体中的溶解，通过形成SiOH/AlOH.3导致网络结构的解聚。揭示水的成分依赖性…铝硅酸盐熔体的更多溶解机制。我们对一系列组合物的系统研究，加上初始计算，揭示了水在（铝）硅酸盐熔体/玻璃中的溶解涉及两个相互竞争的过程：(1)SiOH/AlOH的形成和网络结构的解聚，以及(2)自由OH的形成和网络结构的聚合，后者更倾向于具有大场强阳离子的解聚组合物。发现四、五、六座标铝在含水钙铝硅酸盐玻璃和镁铝硅酸盐玻璃中共存。高压含水矿物的核磁共振研究。对高压含水矿物也进行了类似的研究。这不仅对理解地幔矿物本身的结构很重要，而且对含水熔体/玻璃的高压行为也很有帮助。^<17>富氧氧化物合成方法的发展。我们成功地合成了^<17>的富氧氧化物，收率高。这对于在有限数量的高压材料上进行^<17>的核磁共振测量是必不可少的。少

The purpose of this study was to unravel the structure of hydrous (alumino)silicate melts (glasses) at high pressure in order to understand the behavior of natural magmas. The main achievements are outlined below:1.Development of multi-nuclear, multi-dimensional NMR techniques. Multi-dimensional NMR techniques are particularly powerful structural tools because of the direct information they provide about atomic connectivities. We have succeeded in a variety of NMR measurements including ^1H DQ (double quantum) MAS NMR, ^<27>Al 3Q (triple quantum) MAS NMR, and ^<27>Al-^1H HETCOR (heteronuclear correlation) and 3QMAS/HETCOR NMR.2.Settling a long-term controversy concerning the water dissolution mechanism in polymerized aluminosilicate melts. By using above techniques, we have confirmed that the dissolution of water in polymerized aluminosilicate melts results in the depolymerization of the network structure through formation of SiOH/AlOH.3.Unraveling the compositional dependency of water … More dissolution mechanisms in aluminosilicate melts. Our systematic study over a range of compositions, coupled with ab intio calculations, has revealed that the dissolution of water in (alumino)silicate melts/glasses involves two competing processes : (1) formation of SiOH/AlOH and depolymerization of the network structure, and (2) formation of free OH and polymerization of the network structure, with the latter favored by depolymerized compositions with cations of large field strength. Four-, five-and six-coordinate Al were found to coexist in hydrous Ca-and Mg-aluminosilicate glasses.4.NMR study of high-pressure hydrous minerals. A similar study was also carried out on high-pressure hydrous minerals. This is not only important for understanding the structures of mantle minerals themselves, but also provided insights into the high-pressure behavior of hydrous melts/glasses.5.Development of synthesis method for ^<17>O-enriched oxides. We have succeeded in synthesizing ^<17>O-enriched oxides with high yield. This is essential for ^<17>O NMR measurements on high-pressure materials of limited quantity. Less