HR: 08:45h
 AN: MR11A-04    [Abstracts]
 TI: Water in MgSiO3 Melt at High Pressure
 AU: * Mookherjee, M
EM: mainak@umich.edu
 AF: University of Michigan, Department of Geological Sciences, CC Little Building, Ann Arbor, MI 48109-1005 United States
AU: Stixrude, L P
 EM: stixrude@umich.edu
 AF: University of Michigan, Department of Geological Sciences, CC Little Building, Ann Arbor, MI 48109-1005 United States
AB: The presence of water is thought to play important role in modifying the equilibrium and transport properties of earth materials including silicate liquids. In our study we want to address the following questions: How does the presence of water modifies density of melts? What is the partial molar volume of water in melts? What structural species of H2O are present at high pressure? In order to address these issues we explore the high pressure behaviour of hydrous MgSiO3 melt with 11 wt% H2O, using first principles molecular dynamics simulation, based on local density approximation (LDA) and the plane-wave-pseudopotential method. The simulations are performed in the canonical ensembles with periodic boundary conditions and a Nose' thermostat. Melting was confirmed by the radial distribution function displaying no long range order. By comparing our results with that of the anhydrous counterpart (Stixrude and Karki, 2005), we find that the partial molar volume of water decreases along the 6000 K isotherm from 18 cm3/mol at 6 GPa to 11 cm3/mol at 18 GPa. The water component is substantially more compressible than the silicate component. The partial molar volume of water is much less than the volume of pure water at the same conditions (Pitzer and Sterner, 1994), indicating a difference in structure. Analysis of our simulations shows a range of H2O species including hydroxyls, water molecules and H-O-H-O groups.
DE: 3900 MINERAL PHYSICS
 DE: 3919 Equations of state
 DE: 3924 High-pressure behavior
 DE: 8411 Thermodynamics (0766, 1011, 3611)
 DE: 8439 Physics and chemistry of magma bodies
 SC: Mineral and Rock Physics [MR]
 MN: Fall Meeting 2005