HR: 0800h
AN: MR31A-0132    [Abstracts]
TI: Equations of State of MgAl2O4 Spinel at High Pressure
AU: * Banigan, E
EM: ejb45@georgetown.edu
AF: Georgetown University, Department of Physics, 3700 O St. NW, Washington, DC 20057 United States
AB: We performed static first-principles calculations using the density functional theory as implemented in the ABINIT package to study the behavior of MgAl2O4 spinel, under pressure. We considered several possible structures for which we computed the enthalpy and the PV relations. The calculations showed that MgAl2O4 undergoes a phase transition sequence from spinel structure (Fd3m) to a mixture of oxides (MgO+Al2O3) to a calcium titanite-type structure (Cmcm) with phase transitions at 14.5 and 44.5 GPa, respectively. The calcium ferrite-type structure, a tetragonally distorted cubic structure, and a cation-defective hexagonal structure are all unstable in the -10 to 150 GPa pressure range. We fit Vinet equations of state for the various phases of MgAl2O4. The results were in fair agreement with previous studies; the bulk moduli, K0, of the cubic spinel and calcium titanite-type structures were determined to be 202 GPa and 220 GPa, respectively.
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005