Spin transition in germanate perovskite and post-perovskite at high pressure

高压下锗酸盐钙钛矿和后钙钛矿的自旋转变

基本信息

批准号：
1836852
负责人：
Thomas Duffy
金额：
$ 41.51万
依托单位：
Princeton University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-02-01 至 2023-01-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1836852&HistoricalAwards=false
关键词：
Spin transition germanate perovskite post

项目摘要

The geological activity at Earth's surface can profoundly affect human societies. It ultimately arises from on-going processes within the planet deep interior. These large-scale processes are in turn controlled by the properties of the constituent minerals of the deep Earth. A mineral's crystal and electronic structures are its most fundamental characteristics, from which all other physical and chemical properties follow. Due to the high pressures (millions of atmospheres) and temperatures (thousands of degrees) of the Earth's mantle, there is limited knowledge of the crystal and electronic structures of minerals residing near its base. This region is primarily composed of silicate minerals that adopt structures known as perovskite and post-perovskite. In this project, the investigator will conduct laboratory experiments on these structures to probe how incorporation of iron affects their properties. He will study magnesium germanates, a class of compounds that are close analogs for the silicate minerals of the deep Earth yet can be studied at pressures and temperatures that are more easily attainable in the laboratory. Through this work, he will provide fundamental knowledge of mineral properties that are needed to interpret geophysical observations and constrain the physical processes in Earth's interior. This project will have implications for the understanding of mantle thermal convection, which drives plate tectonics at the origin of numerous hazards for human societies, and provide insights on the effect of extreme conditions of pressure and temperature on materials properties. The project will also provide support for the training of a graduate studentIron influences key physical properties of lower mantle minerals including density, elasticity, element partitioning, and electrical and thermal conductivity. These properties in turn affect the interpretation of seismic and other geophysical observations and constrain models of the deep Earth. Perovskites and post-perovskites are major structures of the lower mantle. Iron in these materials may adopt different valences and spin states and may occupy different structural sites. High-pressure synchrotron Mossbauer spectroscopy and X-ray emission spectroscopy are the primary tools for investigating the electronic state of iron in mantle minerals. In this study the investigator will use these techniques together with conventional Mossbauer spectroscopy to explore the properties of perovskites and post-perovskites over a range of pressures and iron and aluminum contents. He will use magnesium gemanate analogs which lower pressure of formation, compared to that of Earth's silicates, will allow investigating the effect of pressure on post-perovskite properties. The expected results will provide strong constraints on the site occupancies, valences and spin states of perovskite and post-perovskite, as well as a direct test of recent theoretical calculations. They will contribute to unveiling the role of iron in perovskite and post-perovskite which is crucial for the unambiguous interpretation of Mossbauer spectra. They will also enable a more comprehensive understanding of spin-pairing behavior in major lower mantle minerals, thus better constraining the properties of Earth's deep mantle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球表面的地质活动会深刻影响人类社会。最终，它是由于地球内部内部的持续过程而产生的。这些大规模过程又受深层矿物质的特性控制。矿物质的晶体和电子结构是其最基本的特征，从中所有其他物理和化学特性都遵循。由于地球地幔的高压（数百万个气氛）和温度（数千度），因此对矿物质的晶体和电子结构的了解有限。该区域主要由硅酸盐矿物质组成，这些矿物质采用了称为钙钛矿和植物后的结构。在该项目中，研究人员将对这些结构进行实验室实验，以探测铁的掺入如何影响其性质。他将研究德国镁，这是一类具有对深地球硅酸盐矿物质的类似类似物的化合物，但可以在实验室更容易达到的压力和温度下进行研究。通过这项工作，他将提供有关矿物质的基本知识，这些知识是解释地球物理观察并限制地球内部物理过程所需的基本知识。该项目将对对地幔热对流的理解有影响，该对流驱动板块构造以许多对人类社会的危害的起源，并就极端压力和温度对材料特性的极端条件的影响提供见解。该项目还将为训练研究生训练提供支持，从而影响较低地幔矿物质的关键物理特性，包括密度，弹性，元素分配以及电导率和导热率。这些特性反过来影响了地震和其他地球物理观察的解释，并限制了深层地球的模型。钙钛矿和植物后是下地幔的主要结构。这些材料中的铁可以采用不同的价值和自旋状态，并可能占据不同的结构位点。高压同步加速器摩斯鲍尔光谱和X射线发射光谱是研究地幔矿物质铁的主要工具。在这项研究中，研究者将使用这些技术与常规的摩斯鲍尔光谱法一起探索钙钛矿和perovskites的特性，并在一系列压力以及铁和铝含量的范围内探索。与地球硅酸盐相比，他将使用镁gemanate类似物，该类似物的形成压力较低，将允许研究压力对磨牙后特性的影响。预期的结果将对钙钛矿和植物后的现场占用率，价值和自旋状态提供强大的限制，以及对最近理论计算的直接测试。它们将有助于揭示铁在钙钛矿和植物后的角色中的作用，这对于对Mossbauer Spectra的明确解释至关重要。他们还将对主要下层矿物质中的自旋施加行为有更全面的了解，从而更好地限制地球深层地幔的特性。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和知识分子的优点和评估来支持的更广泛的影响审查标准。