HR: 0800h
AN: MR31A-0126    [Abstracts]
TI: A High-Pressure Phase Transition of Calcite-III
AU: * Catalli, K C
EM: krystle@mit.edu
AF: University of California, Santa Cruz, Department of Earth Sciences 1156 High Street, Santa Cruz, CA 95064 United States
AU: Williams, Q
MR31A-0126 AF: University of California, Santa Cruz, Department of Earth Sciences 1156 High Street, Santa Cruz, CA 95064 United States
AB: We document the presence of a high-pressure phase transition in metastable calcite-III using infrared spectroscopy. The post-calcite-III transition initiates at a pressure of 15.5 (±2) GPa, and is completed between 25 and 30 GPa. The transition is particularly apparent in the ν₄-in-plane bending vibration of the carbonate group, in which two new peaks gradually supplant the doublet associated with calcite-III. Furthermore, both the ν₃-asymmetric and ν₁-symmetric stretches of the carbonate group in the high-pressure phase appear at considerably lower frequencies than the extrapolated positions of the corresponding calcite-III peaks. The geometry of the carbonate unit within the high-pressure phase is likely closer to trigonal symmetry than in the calcite-III structure, and the C-O bond is probably longer than in the lower pressure calcite-III phase.
DE: 3900 MINERAL PHYSICS
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005