HR: 0800h
AN: MR11A-0892    [Abstracts]
TI: The Compression of Perovskites
AU: * Zhao, J
EM: jzhao@vt.edu
AF: Jing Zhao, Dept. Geoscience,Virginia Tech, Blacksburg, VA 24061 United States
AU: Ross, N L
EM: nross@vt.edu
AF: Jing Zhao, Dept. Geoscience,Virginia Tech, Blacksburg, VA 24061 United States
AU: Angel, R J
EM: rangel@vt.edu
AF: Jing Zhao, Dept. Geoscience,Virginia Tech, Blacksburg, VA 24061 United States
AB: While silicate perovskite is the dominant phase in the Earth's mantle, very little is known about its detailed structural state and most inferences are based upon the assumption that the silicate octahedra are incompressible. Recent advances in laboratory based single-crystal techniques for measuring the intensities of diffraction from crystals held at high pressures in the diamond-anvil cell have been used to determine the role of polyhedral compression in the response of the ABO3 perovskite structure to high pressures. All perovskites studied exhibit compression of the BO6 octahedra. We have been able to show that when the BO6 octahedra are less compressible than the AO12 sites the octahedra become more tilted with increasing pressure [1]. When the BO6 octahedra are more compressible than the AO12 sites the structure becomes less tilted and evolves towards a higher-symmetry configuration [2]. We have developed a new model, based on the bond valence concept, that successfully predicts the relative compressibilities of the cation sites in most oxide perovskites [3] and hence their response to pressure. The possibilities for extending these measurements to higher pressures will be reviewed. [1] Zhao, J., Ross, N. L. & Angel, R. J. (2004). Phys Chem Miner. 31, 299-305. [2] Ross, N. L., Zhao, J. & Angel, R. J. (2004). J. Solid State Chemistry 177,1276-1284. [3] Zhao, J., Ross, N. L. & Angel, R. J. (2004). Acta Cryst. B60, 263-271.
DE: 3924 High-pressure behavior
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting