Theory of thermoelastic properties of iron bearing minerals

矿物和熔体的热弹性特性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。在过去的十年里，我们在计算地球内部极端条件下材料弹性特性的能力上取得了巨大的进步，我们只使用自然的基本常数作为输入。然而，巨大的挑战仍然存在，特别是在含铁矿物方面。在氧化物和硅酸盐中，铁具有磁矩，它的电子是紧密相关的。具有强相关电子的物质已经挑战了理论家半个多世纪，地幔矿物是其中最复杂的。此外，必须了解它们在极端压力和温度条件下的行为，这些条件会改变它们的磁性状态，这种现象被称为自旋跃迁。在这项资助下，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：铁方石、镁铁硅酸盐钙钛矿和后钙钛矿。Fe2O3是核幔边界可能存在的稳定相，是测试新方法的理想材料。将研究原子振动、原子扩散和集体磁激发，以阐明这些相和地幔的热、弹性、流变和输运性质。这项研究的结果将为研究地幔的状态和演化的研究人员提供重要的输入。这些新方法的发展尤其受到矿物物理学的刺激，已经在开源的initio材料模拟包Quantum ESPRESSO中实现。它们将在该包的后续版本中提供给矿物物理和材料界。pi深入参与教育和推广项目，包括a)培训研究生和博士后，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)向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.