HR: 08:15h
AN: MR41A-02 INVITED     [Abstracts]
TI: Study of sound velocities of hcp-Fe with nuclear resonant inelastic x-ray scattering in a laser-heated diamond cell
AU: * Lin, J
EM: j.lin@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington DC, DC 20015 United States
AU: Sturhahn, W
EM: sturhahn@aps.anl.gov
AF: Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Zhao, J
EM: jzhao@aps.anl.gov
AF: Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Shen, G
EM: shen@cars.uchicago.edu
AF: The University of Chicago, 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Mao, H
EM: mao@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington DC, DC 20015 United States
AU: Hemley, R J
EM: hemley@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington DC, DC 20015 United States
AB: Iron is the most abundant component in the Earth's core. Understanding the physical properties of Fe under core conditions is essential for interpreting the seismological and geomagnetic observations deep in the Earth's interior. The physical properties of Fe have been extensively studied by theoretical calculations and dynamic and static high-pressure experiments, but direct static measurements of the sound velocities of iron under high pressures and temperatures are still lacking. We have studied hcp-Fe with nuclear resonant inelastic x-ray scattering technique in a laser-heated diamond anvil cell. Phonon density of states and sound velocities of hcp-Fe have been measured up to 70 GPa and 1700 K. We found that temperature has a strong effect on the sound velocities; the compressional (V$_{P}$) and shear wave velocities (V$_{S}$) of hcp-Fe decrease significantly with increasing temperature under high pressures. We note that our measurements in VS are relatively insensitive to the differences in the EOS data used in deriving the sound velocities. Therefore, the NRIXS technique is particular good at constraining V$_{S}$ with a precise measurement of V$_{D}$. Thermodynamic, elastic, and vibratonal properties of hot dense hcp-Fe have also been obtained from the measured phonon density of states. Our results have important implications for understanding the sound velocities of the Earth's inner core as well as the fundamental physical properties of iron under extreme pressures and temperatures.
DE: 8115 Core processes (1507)
DE: 7207 Core and mantle
DE: 3924 High-pressure behavior
DE: 3939 Physical thermodynamics
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting