Grain Boundary Diffusion in the Mantle: An Integrated Theoretical and Experimental Study of MgO

原子沿着矿物颗粒之间的边界输运是一个基本的但知之甚少的过程，它在许多重要的地质现象中起着重要的作用，从地震产生的地震能量的衰减到与地幔对流和板块构造有关的许多变形和化学输运过程。该项目支持MgO（地球深部地幔的主要成分）晶界扩散的理论和实验研究。 这项研究的结果将提高估计地球深部晶界化学迁移率和相关地球物理和地球化学性质的能力。 实验和理论相结合的研究计划将专门针对涉及晶界扩散的原子级机制，以及压力，化学杂质和晶界结构对元素迁移率的影响。将使用扩散偶实验、第一性原理和经典分子动力学模拟来确定晶界扩散系数及其对温度、压力以及钙和硅的存在的依赖性。 理论模拟将提供关键信息的扩散机制（S），晶界运输晶界结构的关系，和外推的晶界扩散数据的高压有关地球？最深的地幔。

Transport of atoms along the boundaries between mineral grains is a fundamental but poorly understood process that plays an important role in many important geological phenomena, from the attenuation of seismic energy produced by earthquakes to the many deformation and chemical transport processes associated with mantle convection and plate tectonics. This project supports a combined theoretical and experimental study of grain boundary diffusion in MgO, a major component of Earth's deep mantle. The results of this study will improve the ability to estimate grain boundary chemical transport rates and related geophysical and geochemical properties of the deep Earth. The combined experimental and theoretical research program will specifically target the atomic-level mechanisms involved in grain boundary diffusion, and the influence of pressure, chemical impurities and grain boundary structure on element mobility. Grain boundary diffusion coefficients, and their dependence on temperature, pressure and the presence of calcium and silicon, will be determined using diffusion couple experiments, and first-principles and classical molecular dynamics simulations. The theoretical simulations will provide critical information on the diffusion mechanism(s), the relation of grain boundary transport to grain boundary structure, and the extrapolation of grain boundary diffusion data to the high pressures relevant to Earth?s deepest mantle.