Thermodynamics, Elasticity and Structures of Crustal and Mantle Silicate Minerals

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The structure, stability and thermal properties of high pressure mineral phases composed of MgO, CaO, SiO2 and A12O3, as well as low pressure phases of SiO2, will be investigated with several theoretical and numerical methods. Interionic/atomic potentials and forces will be derived from first principles pseudopotential calculations and electron gas theories. The principal aim of the project is to explore possible phase relationships of minerals that might be found in the earth's mantle and crust, and to examine their elastic properties. Of particular interest is the interplay between pressure and temperature effects on seismic velocities, and the examination of high temperature phases related to (mg,Fe)SiO3 perovskite and products of solid solution with CaSiO3 perovskite and A12O3. Another major goal is the development of parametric Hamiltonian models of covalent bonding in silicate phases present in the crust and upper mantle. A collateral goal is the development of present computational techniques into a form that can be used profitably by nonexperts.