Theoretical Investigations of Mantle Materials

本方案是利用第一性原理理论方法对地幔矿物进行研究和模拟。这项工作的目标是：(1)使预测有助于固体地球的建模和解释尚未获得数据的地震数据；(2)更好地理解矿物行为并帮助解释实验数据；(3)为实验设计提供指导。术语“第一性原理”意味着没有直接使用实验数据；性质是从基础物理学中计算出来的，使用原子核及其电荷的位置作为基本输入。甚至原子核的位置也可以被优化，或者允许在有限的温度下动态移动。然而，基本问题和初始配置通常来自实验数据或观察。这项研究不是代替实验，而是与实验研究相结合。第一原理方法的优点包括发现实验问题或发现理论和数据不一致的新物理的可能性，以及提供目前可获得的实验制度之外的临时数据或由于此类实验的困难而无法获得数据的可能性。建议如下：(1)研究了方长石与浮思体（Mg, Fe1-x）O、硅酸盐钙钛矿（Ca,Mg,Al,Si,Fe）2O3之间重要固溶体的状态、热弹性和相稳定性的热方程；和过渡带石榴石（Ca,Mg,Al）3(Al,Fe,Mg)2 (Si,Al)3O12(2)利用最先进的电子结构方法，如LDA+U和动态平均场理论（DMFT）研究含铁氧化物和硅酸盐在高压下的行为；(3)研究硅酸盐钙钛矿中的扩散。将使用多种方法。势能模型将适合密度泛函理论计算，允许在地球深处的温度和压力下进行分子动力学（MD）模拟。将使用超胞和准随机结构以及有效哈密顿量和蒙特卡罗簇展开来研究固体解。含铁系统将使用超越常规能带理论的方法进行研究；特别是PI将研究Fe1-xO浮士体，赤铁矿Fe2O3和磁铁矿Fe3O4及其高压晶型，以便更好地了解亚铁和三铁在高压和高温下的行为。我们将特别关注铁、铝和空位在硅酸盐钙钛矿中的行为，它们已被证明对钙钛矿的弹性有重要影响。扩散和有限温度弹性将研究使用自由能积分在md -

EAR-0310139This proposal is to use first-principles theoretical methods to study and simulate the minerals of the Earth's mantle. The goal of this work is to (1) make predictions useful for modeling of the solid Earth and interpretation of seismic data where data are not yet available (2) better understand mineral behavior and help in interpreting experimental data and (3) provide guidance for the design of experiments. The term "first-principles" means that no experimental data are directly used; properties are computed from fundamental physics using as basic input the positions of the atomic nuclei and their charges. Even the positions of the nuclei can be optimized, or allowed to move dynamically at finite temperatures. Nevertheless, the basic problems and starting configurations generally come from experimental data or observations. This research is not instead of experiments, but rather works together with experimental studies. The advantages of first-principles methods include the possibility of detecting problems with experiments or discovering new physics, where theory and data disagree, and providing provisional data outside the currently accessible experimental regime or when data are not yet available due to the difficulty of such experiments. The following are proposed: (1) To study the thermal equations of state, thermoelasticity, and phase stability of the important solid solutions between periclase and wustite (Mg, Fe1-x)O, silicate perovskite (Ca,Mg,Al,Si,Fe)2O3, and transition zone garnets (Ca,Mg,Al)3(Al,Fe,Mg)2 (Si,Al)3O12 (2) To study the behavior of iron-bearing oxides and silicates at high pressures using state-of-the-art electronic structure methods such as LDA+U and dynamical mean field theory (DMFT) and (3) To study diffusion in silicate perovskite.A variety of methods will be used. Potential models will be fit to density functional theory computations allowing molecular dynamics (MD) simulations at the temperature and pressures of the deep Earth. Solid solutions will be studied using supercells and quasi-random structures as well as effective Hamiltonians and cluster expansions with Monte Carlo. Iron-bearing systems will be studied using methods that go beyond conventional band theory; in particular the PI will study Fe1-xO wustite, hematite Fe2O3, and magnetite Fe3O4 and their high-pressure polymorphs in order to better understand the behavior of ferrous and ferric iron at high pressures and temperatures. Special attention will be paid to the behavior of Fe, Al, and vacancies in silicate perovskite, which have been shown to have major effects on the elasticity of perovskite. Diffusion and finite temperature elasticity will be studied using free-energy integrations within MD.--