Raman Spectroscopy Under Simultaneous High Pressure - High Temperature in a Laser Heated Diamond Cell: Thermal Pressure, Heat Capacity, Entropy, Thermal Expansivity, and Anharmonic

激光加热金刚石池中同时高压-高温下的拉曼光谱：热压、热容、熵、热膨胀率和非简谐

• 批准号: 0509908
• 负责人: Anastasia Chopelas
• 金额: $ 24.93万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0509908&HistoricalAwards=false
• 关键词: Raman; Spectroscopy; Under; Simultaneous; Pressure

The proposed work consists of the measurement of vibrational modes of minerals at various pressure and temperature conditions, which allows thermodynamic characterization of this mineral through statistical methods or vibrational modeling. Useful information obtained so far using vibrational modeling includes the pressure derivatives of heat capacities, entropies, thermal expansivities, and sound velocities. One important result has not yet been fully exploited: Thermal pressure at a given P and T may be derived using vibrational modeling of internal energy, from PTH = gEvib/V. Thus, vibrational studies at simultaneous high pressure and temperature allow computation of the equation of state, which will support the many x-ray diffraction studies of the thermal equation of state of minerals. Vibrational modeling will also help provide a means for extrapolation beyond the range of the measurements of all thermodynamic properties. Magnetic and electronic contributions to heat capacity and entropy for iron-bearing minerals (or any others with transition metals) will be explored. The proposed laboratory work consists of the development of Raman spectroscopy in the laser heated diamond anvil cell. The efforts will concentrate on the correlation between vibrational spectra and the equations of state of key mantle phases, but will also include the other key thermoelastic parameters. A small, single monochromator system for in situ measurements of temperature is requested. We propose to extend the current Raman spectroscopic capabilities in our laboratory at UW to allow simultaneous high temperatures and pressures using CO2 laser heating in the diamond anvil cell. Once the instrument is in place, geophysically important minerals whose thermal equations of states have been determined by x-ray diffraction will be studied, including MgSi perovskite and forsterite and its high pressure poly-morphs as well as the other MgSiO3 phases. In addition to the first-order goal of obtaining Raman at simultaneous high pressures and temperatures, in situ laser heating in the diamond anvil cell will provide other useful data: phase boundaries where appropriate will be determined in situ and any unquenchable phases can be detected, with probable structures or space groups identified based on Raman spectral patterns.Volume is the parameter against which many other properties are scaled in many temperature, compositional and dynamical models of the Earth's interior. V(P,T) at all deep Earch conditions as well as heat capacity and entropy at pressure will be invaluable to workers in many branches of geoscience and physics, including geophysics, geodynamics, mineralogy, and petrology as well as condensed matter physics. The PI has hosted six of undergraduate researchers, including two women, to participate in research in the laboratory. The PIs current graduate student is a Native American woman, one of the very few to obtain a Ph.D. in any field.

所提出的工作包括测量矿物在不同压力和温度条件下的振动模式，从而允许通过统计方法或振动建模来表征这种矿物的热力学特性。到目前为止，使用振动建模获得的有用信息包括热容、熵、热膨胀率和声速的压力导数。一个重要的结果还没有得到充分的利用：在给定的P和T处的热压力可以使用内部能量的振动模型，由PTH = gEvib/V推导出来。因此，同时在高压和高温下的振动研究允许计算状态方程，这将支持矿物热状态方程的许多x射线衍射研究。振动建模也将有助于提供一种超越所有热力学性质测量范围的外推方法。将探讨磁性和电子对含铁矿物（或任何其他含过渡金属的矿物）的热容和熵的贡献。提出的实验室工作包括在激光加热的金刚石砧细胞中发展拉曼光谱。这些工作将集中在振动谱与地幔关键相的状态方程之间的相关性上，但也将包括其他关键的热弹性参数。需要一种小型的单色仪系统用于现场温度测量。我们建议在西澳大学的实验室扩展目前的拉曼光谱能力，以允许在金刚石砧细胞中使用二氧化碳激光加热同时高温和高压。一旦仪器就位，地球物理上重要的矿物，其状态的热方程已经由x射线衍射确定，将被研究，包括镁硅钙钛矿和橄榄石及其高压多晶体，以及其他MgSiO3相。除了在同时高压和高温下获得拉曼的第一阶目标之外，金刚石砧细胞中的原位激光加热将提供其他有用的数据：原位确定相边界，可以检测到任何不可淬灭的相，并根据拉曼光谱模式确定可能的结构或空间群。在地球内部的许多温度、成分和动力学模型中，体积是衡量许多其他性质的参数。所有深地条件下的V（P，T）以及压力下的热容和熵对于地球科学和物理学许多分支的工作者来说都是无价的，这些分支包括地球物理学、地球动力学、矿物学、岩石学以及凝聚态物理学。PI已经接待了六名本科生研究人员，其中包括两名女性，参与实验室的研究。该学院目前的研究生是一名美国土著妇女，是在任何领域获得博士学位的少数人之一。