High-Pressure Crystal Chemistry and Compressibility of Hydrous Mantle Phases

中子和X射线衍射方法将用于研究在上地幔和过渡带内的温度和压力下稳定的含水相的高压晶体化学、氢键和压缩性。实验将侧重于合成和天然系统，包括致密的含水镁硅酸盐（wadsleyite，E相和OH-斜腐植岩），绿帘石，OH-黄玉和水石榴石。这项工作的结果将显示如何结构纳入水（氢）影响地幔压力下的含水相的行为。智力优势：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，氢也会对地球物质的稳定性和物理性质产生巨大影响。在宏观水平上，体积的压力依赖性（状态方程）用于计算密度和热力学参数，并将半经验氢键模型外推到高压。更广泛的影响：减轻地震灾害的战略是基于地质模型的发展，部分，从实验数据的稳定性和性质的含水相俯冲板。三名本科生和一名研究生将直接参与实验，或学习如何分析晶体学数据和制定模型来解释测量结果。在可能的范围内，这项工作的结果还将传播给为科学和非科学专业设计的本科课程的学生，并通过大学赞助的社区外展计划传播给9-12年级的学生。 的博士该项目资助学生将参加化学物理和地球科学的跨学科学位课程。PI的互动凝聚态物质和无机化学的研究生将有助于加强大学乃至该地区的跨学科研究。

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.