Compression Mechanisms of Upper Mantle Minerals

这个项目将研究包括辉石、石榴石和橄榄石在内的重要上地幔矿物伴随挤压的原子尺度机制。实验工作将包括获得各种辉石和石榴石的晶体结构和拉曼光谱，压力到40 Gpa，中等温度低于550℃。使用这些数据和从文献中获得的数据，将使用当前的电子密度模型来检查结构，以了解成键的变化，特别是辉石中桥联的Si-O-Si键和石榴石中的Si-O-M键(M=八面体阳离子)。我们将对骨架修饰剂的压力效应有一个大致的理解。此外，将模拟O-O相互作用，以研究最紧密堆积晶格对压力的响应。这些模型将有助于我们理解上地幔条件下结晶相的性质。它们还将为了解骨架修饰剂对各种重要工业材料(如沸石和非线性光学行为，如KTP)的影响提供一般背景。

9903104DownsThis project will investigate the atomic scale mechanisms that accompany compression for the important upper mantle minerals including pyroxenes, garnets and olivines. The experimental work will involve obtaining the crystal structures and Raman spectra of various pyroxenes and garnets at pressures to 40 GPa, as well as at modest temperatures below 550 C. Using this data, as well as those obtained from the literature, the structures will be examined with current electron density models to understand bonding changes, especially around the bridging Si-O-Si linkages in pyroxenes and the Si-O-M linkages in garnets (M = octahedral cation). A general understanding of the pressure effect of framework modifiers will be developed. Furthermore, O-O interactions will be modeled in order to investigate the response of the closest-packed lattice to pressure. These models will aid our understanding of the nature of crystalline phases at conditions of the upper mantle. They will also provide a general background to understanding the influence of framework modifiers on all sorts of important industrial materials such as zeolites and non-linear optical behavior, (e.g. KTP).