High-pressure Behavior of Framework Minerals

智力优势。常见的骨架矿物，如菱晶石和钙钛矿分别是地壳和下地幔的普遍存在的组成部分，但由于其复杂的行为，特别是在高压下，它们的结构和性质仍然知之甚少。在之前两次NSF-1000赠款的支持下，PI通过开发非常精确的单晶X射线衍射技术来测量高压下结构的微小变化，对尖晶石和钙钛矿的高压行为有了重要的了解。这项工作导致了一个模型，成功地预测纯端元矿物的相关系和密度。需要资金将这项工作扩展到更天然的长石和钙钛矿固溶体，以阐明各种元素和缺陷替代对弹性和热力学性质的替代机制和影响。拟议项目将支持三项新的重要举措：1.确定控制其他重要骨架矿物压缩的晶体化学原理.从电子密度计算中获得对这些原理的原子尺度的理解。研究骨架矿物的动力学及其在弹性中的作用。技术的发展将继续进一步改进高压下结构的测定。拟议的研究将有助于实现一个最终目标，即开发一个晶体化学“工具箱”，以预测框架矿物的结构演变作为压力、温度和成分的函数。该研究计划将培养各级科学家，包括本科生，研究生，博士后科学家和合作的高级研究人员。个人研究构成了本科生研究项目的基础。研究生在晶体学和矿物物理学方面得到充分的培训，并有机会参观其他实验室和国家设施。通过对弗吉尼亚理工大学的研究访问，培训机会扩大到其他大学的研究生。博士后有机会发展他们的研究技能，并在实验室监督和培训学生。该补助金的授予还将使跨学科的外联活动，包括从区域本科院校的学生和教师举办夏季结晶学研讨会的延续。框架结构由于其有趣的技术特性而引起了人们极大的兴趣。例如，钙钛矿通常用作电子材料，包括超导体、铁弹性体和铁电器件材料。对影响钙钛矿结构状态的因素的研究引起了地球科学界以外的兴趣，预计利用该资助获得的成果将在材料科学和工程中得到应用。

Intellectual Merit. Common framework minerals, such as feldspars and perovskites are ubiquitous components of the Earth's crust and lower mantle, respectively, but their structures and properties remain poorly understood because of their complex behavior, especially at high pressure. With the support of two previous NSF-EAR grants, the PIs have gained significant insight into the high-pressure behavior of feldspars and perovskites via development of very precise single-crystal X-ray diffraction techniques to measure small changes in structures at high pressures. This work resulted in a model that successfully predicts phase relations and densities of the pure end member minerals. Funding is requested to extend this work to more natural feldspar and perovskite solid solutions in order to elucidate substitution mechanisms and effects of various element and defect substitutions on elastic and thermodynamic properties. The proposed project will support three new, important initiatives:1. To determine the crystal chemical principles that control compression of other important groups of framework minerals.2. To gain an atomic-scale understanding of these principles from electron density calculations.3. To investigate the dynamics of framework minerals and their role in elasticity.Technical developments will continue to further improve structure determinations at high pressures. The proposed research will contribute towards an ultimate goal to develop a crystal chemical "toolbox" to predict the structural evolution of framework minerals as a function of pressure, temperature and composition.Broader Impacts. This research program will train scientists at all levels, including undergraduates, graduates, postdoctoral scientists and collaborating senior research faculty. Individual studies form the basis of research projects for undergraduates. Graduate students are fully trained in crystallography and mineral physics and are provided opportunities to visit other laboratories and national facilities. Training opportunities are extended to graduate students from other universities through research visits to Virginia Tech. Post-docs are given the opportunity to develop their research skills, and also supervise and train students in the laboratory. The award of this grant will also enable continuation of inter-disciplinary outreach activities, including hosting of a summer crystallography workshop for students and faculty from regional undergraduate institutions. Framework structures attract great interest because of their interesting technological properties. Perovskites, for example, are commonly used as electronic materials, including superconductors, ferroelastics and ferroelectric device materials. Research on the factors that influence the structural state in perovskites has attracted interest outside the earth science community and it is expected that results obtained with this grant will have application in materials sciences and engineering.