HR: 1340h
AN: MR23B-0060    [Abstracts]
TI: Post Rh₂O₃(II) transition and the high-PT phase diagram of alumina
AU: * Tsuchiya, J
EM: junt@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan
AU: Tsuchiya, T
EM: takut@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan
AU: Wentzcovitch, R M
EM: wentzcov@cems.umn.edu
AF: Department of Chemical Engineering and Materials Science, Minnesota Supercomputing Institute for Digital Technology and Advanced Computations, University of Minnesota, 421 Washington Av SE, Minneapoils, MN 55455 United States
AB: The high-pressure behavior of alumina has been investigated by first-principles computations throughout the range of calibration of the ruby pressure scale. It is found that at 0 K the transformation from corundum to Rh₂O₃(II)-type alumina at ~90 GPa is followed by a second one to the CaIrO₃ structure at ~150 GPa. Quasiharmonic free-energy calculations show that both transformations display negative Clapeyron slope, which is a consequence of the decrease in polyhedral connectivity along the structural sequence. Like the first transformation, the second one should also have significant effects on the ruby pressure scale, especially if ruby is cycled across the phase boundaries. Also metastable perovskite to postperovskite transition was found at 0 K and ~110 GPa slightly higher than the transition pressure in MgSiO₃. Research supported by JSPS, NSF/ITR 0428774, VLab, Ehime Univ Project Fund
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3900 MINERAL PHYSICS
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3939 Physical thermodynamics
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005