Theory of thermoelastic properties of iron bearing minerals

矿物和熔体的热弹性性质是将地球内部的地震层析成像图像转化为具有地球物理意义的信息（矿物学、成分和温度）的关键环节。在过去的十年中，我们在计算地球内部极端条件下材料弹性特性的能力方面取得了巨大的进步，仅使用自然界的基本常数作为输入。然而，仍然存在巨大的挑战，特别是在含铁矿物方面。在氧化物和硅酸盐中，铁具有磁矩，其电子具有强相关性。半个多世纪以来，具有强关联电子的物质一直是理论界的难题，地幔矿物是其中最复杂的一类。此外，它们的行为必须在压力和温度的极端条件下理解，这会改变它们的磁性状态，这种现象称为自旋跃迁。根据这项授权，基于DFT+U方法的新方法将被应用于研究自旋跃迁及其对地球下地幔最重要相的热弹性性质的影响：铁方镁石，铁镁硅酸盐钙钛矿和后钙钛矿。Fe_2O_3可能是核幔边界的稳定相，是检验新方法的理想材料。原子振动，原子扩散和集体磁激发将被研究，以阐明这些阶段和地幔的热，弹性，流变和运输性能。这项研究的结果将是研究人员调查地幔状态和演化的重要投入。新的方法，其发展正在刺激，特别是矿物物理学，已在开源的从头材料模拟包量子ESTERO。这些资料将在矿物物理学和材料界随后发行的成套资料中提供。PI深入参与教育和推广计划，包括a）研究生和博士后培训，B）通过明尼苏达超级计算研究所提供的暑期实习培训本科生，以及c）为材料和矿物物理社区提供教程。

Thermoelastic properties of minerals and melts are the crucial link that permit seismic tomography images of the Earth's interior to be translated into information of geophysical significance: mineralogy, composition, and temperature. Over the last decade, enormous advances have been made in our ability to compute elastic properties of materials under the extreme conditions of Earth's interior using only the fundamental constants of nature as input. Nevertheless, great challenges remain, especially regarding iron bearing minerals. In oxides and silicates, iron has magnetic moment and its electrons are strongly correlated. Materials with strongly correlated electrons have challenged theorists for more than half century and mantle minerals are among the most complex of them. Besides, their behavior must be understood at extreme conditions of pressures and temperatures, which change their magnetic state, a phenomenon known as spin transition. Under this grant novel methods based on the DFT+U approach will be applied to investigate spin transitions and its consequences for the thermoelastic properties of the most important phases of Earth's lower mantle: ferropericlase, ferromagnesium silicate perovskite and postperovskite. Fe2O3 is a possible stable phase at the core-mantle boundary and an ideal material for testing the new methods. Atomic vibrations, atomic diffusion, and collective magnetic excitations will be studied to shed light on the thermal, elastic, rheological, and transport properties of these phases and of the mantle. The outcome of this research will be essential input for researchers investigating the state and evolution of the mantle. The novel methods, whose development is being stimulated especially by mineral physics, have been implemented in the open source at initio materials simulation package Quantum ESPRESSO. They will be available in subsequent releases of the package to the mineral physics and materials communities. The PIs are deeply involved with education and outreach programs that include a) training of graduate students and post-docs, b) training of undergraduates through summer internships offered through the Minnesota Supercomputing Institute, and c) giving tutorials to the materials and mineral physics community.