Calorimetry Under Extreme Conditions

地球内部处于高温高压状态，导致矿物的结构转变。必须测量所涉及材料的热力学性质，以正确约束和模拟导致板块构造、火山作用和地震的化学过程。该项目开发和应用新的方法来测量与矿物反应相关的热效应，重点放在三个方面：研究在几十万个大气压下制备的非常小的样品，在岩石熔化的温度下直接测量反应热（1000 - 2500摄氏度），以及测量硫化物的能量学，这对金属矿石和地球深部及陨石很重要。这些实验依赖于专门和独特的量热法。（热测量）设备，可在Navrotsky的热化学设施在加州大学戴维斯分校和弗朗西斯赫尔曼，在加州大学伯克利分校的合作者的实验室。将使用伯克利的硅芯片上的微机械量热计测量高压相的微克大小的样品的热容，所述硅芯片已被用于固态物理社区的薄膜和小晶体。它们在高压矿物相中的应用需要一些技术上的改进和发展。高温下的工作将依赖于戴维斯的一套定制和商业热量计。在高压硅酸盐相（尖晶石，wadsleyite，钙钛矿，石榴石等）的热容和磁转变将通过芯片上的量热法测量。从这些测量中得到的熵将与其他热力学数据相结合，以提供对地球地幔相化学的严格约束。测定了铁-硫和铁-镍-硫体系中各相的生成热。高温相变和熔化的氧化物和硅酸盐的数量将被表征。这些不同的数据将被用来了解地球上发生的高温过程。这些数据也在高温材料加工、陶瓷、冶炼和精炼中有应用。对热力学参数的基本理解将分子水平的结构与宏观性质联系起来，并为理论计算提供基准。

The interior of the Earth is at high temperature and high pressure, leading to structural transformations in the minerals present. The thermodynamic properties of the materials involved must be measured to properly constrain and model the chemical processes leading to plate tectonics, volcanism, and earthquakes. This project develops and applies new methodology for measuring the heat effects associated with mineral reactions, with emphasis in three areas: the study of very small samples prepared at pressures of several hundred thousand atmospheres, the direct measurement of heats of reactions at temperatures where rocks melt (1000 - 2500 degrees Centigrade), and the measurement of energetics of sulfides, important to metal ores and to the deep Earth and meteorites.The experiments rely on specialized and unique calorimetric (heat measuring) equipment, available in Navrotsky's Thermochmistry Facility at UC Davis and in the laboratories of Frances Hellman, a collaborator at UC Berkeley. The heat capacities of microgram sized samples of high pressure phases will be measured using micromachined calorimeters on a silicon chip at Berkeley, which have been used in the solid state physics community for thin films and small crystals. Their application to high pressure mineral phases requires some modification and development of techniques. The work at high temperature will rely on a suite of custom built and commercial calorimeters at Davis. The heat capacities and magnetic transitions in high pressure silicate phases (spinel, wadsleyite, perovskite, garnet, and others) will be measured by calorimetry on a chip. The entropies derived from these measurements will be combined with other thermodynamic data to provide tight constraints on the phase chemistry of the Earth's mantle. The heats of formation of phases in the iron-sulfur and iron-nickel sulfur system will be measured. High temperature phase transitions and melting in a number of oxides and silicates will be characterized. Together, these various data will be used to understand high temperature processes occurring in the Earth. The data also have applications in high temperature materials processing, ceramics, smelting and refining. A fundamental understanding of thermodynamic parameters links structure on the molecular level with macroscopic properties and provides benchmarking for theoretical calculations.