Prewitt/Hazen/Finger The dynamic history and present state of the Earth's interior result from properties of earth materials; detailed understanding of earth processes depend fundamentally on structural characterization of these materials at high pressures and temperatures. The Geophysical Laboratory has been a pioneer in developing techniques for in-situ diffraction studies on both single crystal and powder samples under extreme conditions. A recent NSF equipment grant supporting the purchase of a new diffractometer with a CCD detector will enable us to measure full three-dimensional diffraction patterns of very small crystals, determine the nature of a range of defects affecting crystal properties, and to collect data rapidly at a series of increasing/decreasing pressures and/or temperatures. Specific experiments will focus on structure investigations of silicates, oxides, and sulfides, hydrogen bonding models for dense hydrous magnesium silicates, cation ordering in multi-cation oxides, and various analog compounds that can provide information about earth processes and materials. We will also continue to provide facilities and support to outside investigators who want to conduct crystallographic experiments, especially at high pressures and temperatures.
