HR: 17:00h
AN: MR34A-05    [Abstracts]
TI: Elastic moduli and equation of state of NaCl to 30 GPa by simultaneous x-ray density and Brillouin sound velocity measurements
AU: * Sinogeikin, S
EM: sinogeik@uiuc.edu
AF: University of Illinois at UC, Geology Dept., 1301 W Green St, Urbana, IL 61801 United States
AU: Lakshtanov, D
MR34A-05 AF: University of Illinois at UC, Geology Dept., 1301 W Green St, Urbana, IL 61801 United States
AU: Sanches-Valle, C
MR34A-05 AF: University of Illinois at UC, Geology Dept., 1301 W Green St, Urbana, IL 61801 United States
AU: Prakapenka, V
MR34A-05 AF: GSECARS, The University of Chicago, Chicago, IL 60637 United States
AU: Shen, G
MR34A-05 AF: HPCAT, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 United States
AU: Gregoryanz, E
MR34A-05 AF: Carnegie Institution of Washington, Geophysical Laboratory, 5251 Broad Branch Rd NW, Washington, DC 20015 United States
AU: Bass, J
EM: jaybass@uiuc.edu
AF: University of Illinois at UC, Geology Dept., 1301 W Green St, Urbana, IL 61801 United States
AB: NaCl is commonly used as a pressure standard in a variety of high pressure experiments. Some recent experimental studies suggest that the commonly used Decker equation of state of NaCl in the B1 structure is outdated and possibly inaccurate at pressures above 15-20 GPa. This would result in erroneous phase diagrams and PVT equations of state of materials when NaCl is used for pressure determination. Moreover, most previous acoustic velocity measurements of NaCl have been limited to pressures below 10 GPa, making the elastic properties of NaCl at higher pressure, especially in the vicinity of B1-B2 transition, highly uncertain. Recently we have constructed a Brillouin spectrometer at GSECARS, APS (station 13-BM-D) which allows accurate simultaneous sound velocity and lattice parameter measurements at high pressures. Such measurements were performed during the commissioning time on single crystal NaCl (B1) to a maximum pressure of 30 GPa in a diamond cell with Ne as a hydrostatic pressure medium. At each pressure we measured the acoustic velocities of NaCl in several crystallographic directions, and also the unit cell parameters. From these measurements we directly obtained the complete set of single crystal elastic moduli, as well as isotropic adiabatic bulk (KS) and shear (μ) moduli. Unit cell parameters of Ne, Au and Pt were measured at each pressure for cross calibration. At high pressure NaCl exhibits a number of unusual properties. First, it shows extreme elastic anisotropy which is 3.3 times higher than that at ambient pressure. Secondly, above ~15 GPa the density-velocity relations deviate from linearity and violate Birch's law. Thirdly, above 20 GPa in the vicinity of B1-B2 transition the acoustic velocities and elastic (especially shear) moduli show unusual behavior that is not adequately described by finite strain equations of state. The above features and implications of our data for the EOS of NaCl will be discussed.
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005