HR: 0830h
AN: V31D-0960    [PDF]
TI: High Pressure Elasticity of Iron Alloys From Nuclear Resonant Inelastic X-ray Scattering and X-ray Diffraction
AU: * Mao, W L
EM: wmao@uchicago.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Avenue, Chicago, IL 60637 United States
AU: Heinz, D L
EM: heinz@geosci.uchicago.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Avenue, Chicago, IL 60637 United States
AU: Campbell, A J
EM: acampbel@uchicago.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Avenue, Chicago, IL 60637 United States
AU: Sturhahn, W
EM: sturhahn@aps.anl.gov
AF: Advanced Photon Source, Argonne National Laboratory 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Ding, Y
EM: y.ding@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Mao, H
EM: mao@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Hemley, R J
EM: hemley@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AB: As major constituents of the Earth's core, Fe and its alloys have long been of great interest to geophysicists. Information on their high-pressure, vibrational dynamic behavior is essential for interpreting seismic observations and for numerical modeling of the Earth's deep interior. Silicon and hydrogen have been suggested as possible lower atomic weight components in the Earth's core. Previous work has shown that the addition of a modest amount of Si to Fe can have a profound effect on the Fe. However, Fe-rich Fe-Si alloys have not been investigated above 100 GPa, thus requiring extrapolation of lower pressure data to core conditions. Hydrogen in the core could have profound implications on the H budget within the Earth and our understanding of the physics and chemistry of the core. X-ray diffraction (XRD) experiments show that stoichiometric FeH is formed at 3 GPa from the reaction of Fe and fluid hydrogen, and this compound is stable to at least 62 GPa. With the limitation of XRD alone, however, important geophysical and crystal chemical information about FeH is still lacking. We have conducted XRD experiments under hydrostatic conditions with He as a pressure-transmitting medium to 50 GPa and under nonhydrostatic conditions to over 200 GPa. We have conducted nuclear resonant inelastic scattering (NRIXS) experiments on FeH to over 50 GPa at ambient temperature. The collected NRIXS spectra have been summed, and converted to a partial (Fe related) phonon density of state (DOS) for final analysis. The initial slope coupled with hydrostatic equation of state data yields VP and VS for comparison to seismic observations for insight into core chemistry and physics.
DE: 3900 MINERAL PHYSICS
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting