Crystal Structures of Minerals at Ultrahigh Pressures and Temperatures

现代行星物理学的一个基本目标是了解行星的结构以及它们在地质时期是如何演化的。 这需要对地球内部不同区域的成分和矿物学有详细的了解，并确定一些重要的化学和物理性质，如可压缩性，熔化温度和流变性。 然而，地球和行星的内部几乎完全隐藏在直接观察之外。 因此，有必要从地球物理观测中推断地球深部的性质，例如从地震中推断地震波速度随深度的变化，并通过实验室实验。 后者是具有挑战性的，因为地球深层内部的压力大约是地球表面的一百万倍，温度可高达5000 K。 激光加热金刚石对顶砧是唯一能够再现地球深部地幔和地核压力-温度条件的实验室技术。 在本项目中，我们将利用该装置与先进光子源的同步辐射装置相结合，对与地幔和地核有关的一些基础物质的性质进行研究，对铁、钼和硫化铁进行高达250 GPa和4000 K条件下的原位X射线衍射实验。 这些结果将提供新的限制相和状态方程的潜在的核心材料，也将有助于解释冲击压缩和静态熔化数据。 最近在接近地球核幔边界的条件下发现的后钙钛矿相对理解该地区的结构和动力学具有重大意义。 我们还将在120 GPa和2500 K的模拟系统（Mg，Fe）GeO 3-Al 2 O3中对钙钛矿和后钙钛矿相进行全面的研究。 我们将研究组成变量（Fe，Al）如何影响状态方程，过渡压力和结构响应的钙钛矿和后钙钛矿多晶型物在这个系统中。最后，我们将研究SiO2在SiO2的压力，以测试理论预测的进一步相变在二氧化硅。该研究计划将通过为研究生和本科生提供高压科学，同步加速器X射线技术，矿物物理学和全球地球物理学的高级培训来加强研究和教育基础设施。 我们的研究将提供有关高压和高温下材料物理学以及行星内部结构和状态的基本新知识

A fundamental goal of modern geophysics is to understand the structure of planets and how they have evolved over geological time. This requires a detailed knowledge of the composition and mineralogy of different regions of the Earth's interior coupled with determination of some important chemical and physical properties such as compressibility, melting temperature, and rheology. However, the interiors of the Earth and planets are almost completely hidden from direct observation. As a result, it is necessary to infer properties of the deep Earth from geophysical observations, such as the variation of seismic wave velocity with depth inferred from earthquakes, and through laboratory experimentation. The latter is challenging as the Earth's deep interior is at pressures approximately one million times greater than that at Earth's surfaces and temperatures can reach up to 5000 K. The laser-heated diamond anvil cell is the only laboratory technique that can reproduce the pressure-temperature conditions in the deep mantle and core of the Earth. In this project, we will use this device in combination with synchrotron radiation facilities at the Advanced Photon Source to study the properties of a number of fundamental materials relevant to the deep mantle and core.For iron, molybdenum, and iron sulfide, we will carry out in situ x-ray diffraction experiments to conditions as high as 250 GPa and 4000 K. These results will provide new constraints on phases and equation of state of potential core materials, and will also aid in the interpretation of shock compression and static melting data. The recent discovery of a post-perovskite phase at conditions approaching the Earth's core-mantle boundary has major implications for understanding the structure and dynamics of this region. We will also carry out a comprehensive study of perovskite and post-perovskite phases in the analog system (Mg,Fe)GeO3-Al2O3 to 120 GPa and 2500 K. We will examine how compositional variables (Fe, Al) affect the equation of state, transition pressures, and structural response of both the perovskite and post-perovskite polymorphs in this system. Finally, we will examine SiO2 at ultrahigh pressures to test theoretical predictions of further phase transitions in silica. This research program will enhance research and education infrastructure by providing advanced training in high-pressure science, synchrotron x-ray techniques, mineral physics and global geophysics to graduate and undergraduate students. Our research will provide fundamental new knowledge about the physics of materials at high pressures and temperatures and the structure and state of planetary interiors