High-Pressure Crystal Chemistry and Compressibility of Hydrous Mantle Phases

中子和X射线衍射法将用于研究上地幔和过渡带内在温度和压力下稳定的水合相的高压晶体化学、氢键和可压缩性。实验将集中在合成和自然系统上，包括致密的水合硅酸镁(Wadsleyite，E相和OH-斜辉石)、绿帘石、OH-黄玉和水榴石。这项工作的结果将显示在地幔压力下，结构上结合的水(氢)如何影响水合相的行为。智力价值：了解氢在含水相高压下的位置和行为特别重要，因为即使在非常小的浓度下，氢也会对地球材料的稳定性和物理性质产生如此巨大的影响。在宏观水平上，利用体积的压力依赖关系(状态方程)计算密度和热力学参数，并将半经验氢键模型外推到高压下。更广泛的影响：减轻地震灾害的战略是以地质模型为基础的，部分是根据关于俯冲板块中水合相的稳定性和性质的实验数据开发的。三名本科生和一名研究生将直接参与实验，或者学习如何分析结晶学数据并建立模型来解释测量结果。在可能的范围内，这项工作的结果也将通过该大学赞助的社区推广计划传播给为理科和非理科专业设计的本科课程的学生，以及9-12年级的学生。由该项目资助的博士生将进入化学物理和地球科学的跨学科学位课程。P.I.和研究生与凝聚态物质和无机化学的相互作用将有助于促进大学内、甚至可能是该地区跨科学学科的研究。

Neutron and X-ray diffraction methods will be used to investigate the high- pressure crystal chemistry, hydrogen bonding and compressibility of hydrous phases stable at temperatures and pressures within the upper mantle and transition zone. Experiments will focus on both synthetic and natural systems, including dense hydrous magnesium silicates (wadsleyite, phase E and OH-clinohumite), epidotes, OH-topaz and hydrogarnet. The results of this work will show how structurally incorporated water (hydrogen) affects the behavior of hydrous phases at mantle pressures. Intellectual Merit: Understanding the location and behavior of hydrogen at high pressure of hydrous phases is particularly important because even at very small concentrations hydrogen has such a dramatic affect on both the stability and physical properties of earth materials. At the macroscopic level, the pressure dependence of the volume (equation of state) is used in the calculation of density and thermodynamic parameters, and to extrapolate semi- empirical hydrogen-bonding models to high pressures. Broader Impacts: Mitigation strategies for earthquake hazards are based on geological models developed, in part, from experimental data on the stability and properties of hydrous phases in subducted slabs. Three undergraduates and one graduate student will participate either directly in the experiments, or learn how to analyze crystallographic data and formulate models to interpret measurements. To the extent possible, the results of this work will also be disseminated to students in undergraduate courses designed for both science and non- science majors, and to grades 9-12 students through community outreach programs sponsored by the university. The Ph.D. student funded by this project will be enrolled in an interdisciplinary degree program in chemical physics and geosciences. Interactions of the P.I. and graduate student with the condensed matter and inorganic chemistry will serve to enhance research across scientific disciplines within the university and, possibly, the region.