Collaborative Research: Quantum Mechanical Modeling of Major Mantle Materials

EAR-0230154Lars Stixrude 翻译地震结构或捕虏体所揭示的深层地质过程记录需要对高压和高温下矿物的基本物理、化学和原子尺度结构有深入的了解。在之前的合作项目中，研究人员开发了一种基于密度泛函理论的地幔材料研究新方法，该方法是对矿物物理学实验工作的补充。他们表明，理论可以提供对物质行为基本原理的见解，这些基本原理构成了我们在有限的实验或理论结果中进行插值和推断到复杂地球的能力的基础。研究人员过去对纯端元相的研究预测了一些特性，这些特性为了解地球内部的性质提供了重要的新见解。在这项提案中，他们转向考虑地幔矿物之间通过相变和化学交换的相互作用。这项研究将首次采用从头计算的方法对地幔固溶体进行理论研究，包括其结构、热化学和物理性质以及相平衡。 研究人员还将继续研究既定的方向，包括热弹性特性的预测。这项研究预计将有助于我们理解：1）通过预测温度和成分对固溶体（包括较低地幔条件下的 Mg-Ca-Al-Fe 钙钛矿）弹性特性的影响，了解地幔横向不均匀性的起源。 2）地震“不连续性”的起源、结构和地球动力学后果，通过预测单组分和多组分相平衡，包括秋元石到钙钛矿的转变，以及伪二元尖晶石到钙钛矿加镁方铁矿的转变。 3）通过预测主要共存相之间的相平衡和元素分配，包括硅酸盐钙钛矿中的Mg-Ca分配和溶出，对可能的过渡带和下地幔起源的样品进行解释。

EAR-0230154Lars StixrudeTranslating the record of deep-seated geological processes as revealed by seismic structure or xenoliths requires sophisticated knowledge of the essential physics, chemistry, and atomic scale structure of minerals at high pressures and temperatures. Over the course of their prior collaborative project, the investigators have developed a new approach to the study of mantle materials based on density functional theory that is complementary to experimental efforts in mineral physics. They have shown that theory can provide insights into the fundamentals of material behavior that form the basis of our ability to interpolate among and extrapolate from necessarily limited experimental or theoretical results to a complex earth. The investigators past studies of pure end-member phases have predicted properties that have lent important new insight into the nature of the earth's interior. In this proposal, they move toward considering the interaction between mantle minerals through phase transitions and chemical exchange.This research will pursue for the first time with ab initio methods the theoretical investigation of mantle solid solutions, including their structure, thermochemistry, and physical properties, and of phase equilibria,. The investigators will also continue with established directions including the prediction of thermoelastic properties. This research is expected to contribute to our understanding of: 1) The origins of lateral heterogeneity in the mantle, through predictions of the effects of temperature and composition on the elastic properties of solid solutions, including Mg-Ca-Al-Fe perovskite at lower mantle conditions. 2) The origin, structure, and geodynamical consequences of seismic "discontinuities", through predictions of one-component and multi-component phase equilibria including the akimotoite to perovskite transition, and the pseudobinary ringwoodite to perovskite plus magnesiowustite transition. 3) The interpretation of samples of possible transition zone and lower mantle origin, through predictions of phase equilibira and element partitioning among major coexisting phases, including Mg-Ca partitioning and exsolution in silicate perovskite.