HR: 11:05h
AN: MR32A-04 INVITED    [Abstracts]
TI: First-Principles Investigation of Melts in the MgO-SiO2 System
AU: * Karki, B B
EM: karki@csc.lsu.edu
AF: Department of Computer Science, Department of Geology and Geophysics, Louisiana State University, 298 Coates Hall, Baton Rouge, LA 70810, United States
AU: de Koker, N P
EM: dekoker@umich.edu
AF: Department of Geological Sciences, University of Michigan, 1100 North University Ave., Ann Arbor, MI 48109, United States
AU: Stixrude, L P
EM: stixrude@umich.edu
AF: Department of Geological Sciences, University of Michigan, 1100 North University Ave., Ann Arbor, MI 48109, United States
AB: We have recently completed simulations of four melt compositions, namely, SiO2, MgSiO3, Mg2SiO4 and MgO within density functional theory. These results allow us to investigate the structural and thermodynamical properties of melts along the MgO-SiO2 join as a function of pressure. In particular, we have found that the mixing in MgO-SiO2 system is substantially nonideal at low pressures with negative excess volume and enthalpy of mixing. With increasing pressure, the volume of mixing decreases rapidly to a value close to zero at pressures above 50 GPa whereas the enthalpy of mixing remains negative. The radial distribution functions and coordination environments are found to show interesting changes with varying composition. Also, the effects of composition on diffusivity are shown to be substantial at low pressures whereas the effects are increasingly suppressed with increasing pressure.
DE: 1037 Magma genesis and partial melting (3619)
DE: 3640 Igneous petrology
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3929 NMR, Mossbauer spectroscopy, and other magnetic techniques
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting