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高压晶体化学、氢键和上地幔和过渡区内稳定的水相的可压缩性。实验将集中于合成系统和自然系统，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结构上结合的水（氢）如何影响地幔压力下含水相的行为。智力优势：了解氢在高压水合相中的位置和行为是特别重要的，因为即使在非常小的浓度下，氢也会对土材料的稳定性和物理性质产生巨大的影响。在宏观水平上，体积的压力依赖性（状态方程）被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所依据的地质模型部分是根据关于俯冲板块中含水相的稳定性和特性的实验数据建立的。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并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理工科和非理工科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。本项目资助的博士生将攻读化学物理和地球科学的跨学科学位课程。私家侦探和研究生与凝聚态物质和无机化学的互动将有助于加强大学内甚至可能是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.