HR: 10:35h
AN: MR12A-02    [Abstracts]
TI: Structure and freezing of MgSiO₃ liquid in Earth's interior
AU: * Stixrude, L
EM: stixrude@umich.edu
AF: University of Michigan, Dept. of Geological Sciences, Ann Arbor, MI 48104 United States
AU: Karki, B
EM: karki@csc.lsu.edu
AF: Louisiana State University, Dept. of Computer Science, Baton Rouge, LA 70803 United States
AB: Silicates liquids are primary agents of mass and heat transport, yet little is known of their physical properties or structure over most of the mantle pressure regime. We have applied density functional theory to the study of silicate liquids via first principles molecular dynamics. The electronic structure, total energy, stress tensor, and forces acting on the atoms are computed self-consistently at each time step and atomic positions advanced according to Newton's equations of motion. The simulations are performed in the NVT ensemble with a Nose thermostat. We find that over the pressure regime of Earth's mantle the mean Si-O coordination number increases nearly linearly with compression from four-fold to six-fold. The Grüneisen parameter of the liquid increases markedly on compression, in contrast to the behavior of mantle crystalline phases, and in accord with expectations based on the pressure-induced change in structure of the liquid. The density contrast between liquid and crystal decreases nearly five-fold over the mantle pressure regime and is 4 % at the core-mantle boundary. The melting curve, obtained via integration of the Claussius-Clapeyron equation yields a melting temperature of 5400 ± 600 K at the core mantle boundary. Our results support the notion of buoyantly stable silicate melts at the core-mantle boundary.
DE: 3924 High-pressure behavior
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8125 Evolution of the Earth (0325)
DE: 8145 Physics of magma and magma bodies
DE: 8439 Physics and chemistry of magma bodies
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005