HR: 1340h
AN: DI53A-1101    [Abstracts]
TI: The Post-Perovskite Transition in NaMgF3 Measured Under an Ar Medium
AU: * Hustoft, J W
EM: jhustoft@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Bldg. 54-615, Cambridge, MA 02139, United States
AU: Catalli, K
EM: krystle@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Bldg. 54-615, Cambridge, MA 02139, United States
AU: Shim, S
EM: sangshim@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Bldg. 54-615, Cambridge, MA 02139, United States
AU: Kubo, A
EM: akubo@cars.uchicago.edu
AF: GSECARS, Argonne National Laboratory, 9700 South Cass Avenue, Bldg. 434A, Argonne, IL 60439, United States
AU: Prakapenka, V B
EM: prakapenka@cars.uchicago.edu
AF: GSECARS, Argonne National Laboratory, 9700 South Cass Avenue, Bldg. 434A, Argonne, IL 60439, United States
AU: Caldwell, W A
AF: Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, MS6R2100, Berkeley, CA 94720, United States
AU: Kunz, M
AF: Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, MS6R2100, Berkeley, CA 94720, United States
AB: Neighborite, NaMgF₃, is isostructural to MgSiO₃ perovskite and has been shown to transform to the CaIrO₃ type (post-perovskite) at much lower pressure and room temperature. We have conducted X-ray diffraction of the post-perovskite transition in NaMgF₃ using argon as a pressure medium at the GSECARS sector of APS and beamline 12.2.2 of ALS. We observe the first appearance of post-perovskite occurring between 37 and 42 GPa during compression at room temperature and a mixed phase of perovskite and post-perovskite was observed up to 49 GPa at room temperature, whereas a complete transition to post-perovskite was documented by previous studies at 19-30 GPa and room temperature with a Si-oil, NaCl, or MgO pressure medium. This difference in pressure may indicate that deviatoric stresses are an important factor in explaining the different observations. In situ double-sided laser heating at GSECARS demonstrated that perovskite transforms completely to pure post-perovskite at ~2000 K and ~47 GPa. We did not observe a new high-temperature phase, N-phase, proposed by Martin (2005) at 37 GPa after heating to 2000 K. We also found that the volume decreases by 2±1% across the post-perovskite transition in NaMgF₃.
DE: 1011 Thermodynamics (0766, 3611, 8411)
DE: 3621 Mantle processes (1038)
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting