HR: 11:20h
AN: MR22A-05    [Abstracts]
TI: Effect of chemistry on the physical properties of perovskite and post-perovskite (Mg,Fe,Al)(Al,Si)O3
AU: * Caracas, R
EM: r.caracas@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, N.W., Washington, DC 20015 United States
AU: Cohen, R E
EM: r.cohen@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, N.W., Washington, DC 20015 United States
AB: Using first-principles calculations we predict the effects of composition on perovskite to post-perovskite transition pressure. The transition is predicted at 110 GPa for pure MgSiO₃. The addition of Al₂O₃ slightly increases this transition pressure, and the addition of Fe²⁺ considerably reduces it; the FeSiO₃ end-member term is stable in the post-perovskite modification with respect to perovskite at all pressures. We find that Fe²⁺ is in high spin in post-perovskite, and the groundstate of FeSiO₃ post-perovskite is antiferromagnetic. We determine the static equations of state, densities, elasticity and seismic wave velocities. At the transition V_p increases slightly, and V_s increases significantly, consistent with the seismic observations for D''. The addition of both Fe²⁺ and Al₂O₃ decrease the seismic wave velocities. For the MgSiO₃ term we compute the Raman powder spectra and compare with available experimental data.
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 8147 Planetary interiors (5430, 5724, 6024)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005