Collaborative Research: Quantum Mechanical Modeling of Major Mantle Materials

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

EAR-0230154 Lars Stixrude Translating 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.