Acquisition of Equipment to Establish a High-Pressure Single-Crystal X-Ray Laboratory

[01:13 . 1979]一个高压、单晶x射线衍射实验室将在路易斯维尔大学建立。现有的完全可操作的CAD4衍射仪将适用于高压金刚石砧细胞。该实验室还将配备一台静电钻孔机和用于装载细胞的立体显微镜，以及一台用于压力校准的激光光谱仪。第二个x射线单元也将升级为固态发生器。安装在该装置上的进动相机将用于检查晶体质量并确定压力单元中单晶的方向。这个新实验室将专门研究高压下的含水矿物。这组地球物质在与地震活动有关的地幔过程中起着重要作用。例如，含水矿物中与相变有关的体积变化与应力的局部化和沿俯冲带发生的地震有关。本项目的实验重点是水合硅酸镁（oh -斜殖石）和水榴石。相平衡研究表明，斜殖岩是俯冲带~400 km深度（过渡带）的稳定含水相。其高压红外光谱在~13 GPa处显示出一些异常。这些异常与相变有关的可能性将使用转换后的CAD4衍射仪系统进行研究。合成无硅水榴石（katoite）已被用作模型，以了解OH如何被纳入地壳和地幔中的硅酸盐石榴石中。在5gpa时，katoite结构发生相变。将用CAD4在高压下收集x射线数据，以确定在天然存在的水榴石中是否观察到类似的转变。* * *

0131979LagerA high-pressure, single-crystal X-ray diffraction laboratory will be established at the University of Louisville. An existing, fully operational CAD4 diffractometer will be adapted for high-pressure use with a diamond-anvil cell. The laboratory will also house an electrostatic drilling machine and stereomicroscope for loading the cell and a laser spectrometer for pressure calibration. A second X-ray unit will also be upgraded with a solid-state generator. A precession camera mounted on this unit will be used as a check on crystal quality and to determine the orientation of single crystals in the pressure cell. The new laboratory will be dedicated to studies of hydrous minerals at high pressure. This group of earth materials plays an important role in mantle processes related to earthquake activity. For example, volume changes associated with phase transitions in hydrous minerals have been linked to the localization of stress and the occurrence of earthquakes along subduction zones. Experiments in this project will focus on hydrous magnesium silicate (OH-clinohumite) and hydrogarnet. Phase-equilbria studies indicate that clinohumite is a stable water-bearing phase in subduction zones to depths of ~400 km (transition zone). Its high-pressure infrared spectrum shows several anomalies at ~13 GPa. The possibility that these anomalies are related to a phase transition will be investigated using the converted CAD4 diffractometer system. Synthetic Si-free hydrogarnet (katoite) has been used as a model to understand how OH is incorporated in silicate garnets that occur in the crust and mantle. The katoite structure undergoes a phase transition at 5 GPa. X-ray data will be collected with the CAD4 at high pressures to determine if a similar transition is observed in naturally occurring hydrogarnets. ***