HR: 1340h
AN: MR23A-0039    [Abstracts]
TI: Composition Dependence of Pressure-Induced Spin Transitions in the (Mg,Fe)O System
AU: * Persson, K A
EM: kpersson@mit.edu
AF: MIT, 77 Massachusetts Ave, Cambridge, MA 02139-4307 United States
AU: Berta, A
EM: akberta@wisc.edu
AF: University of Wisconsin - Madison, 244 Materials Science & Engineering 1509 University Avenue, Madison, WI 53706-1595 United States
AU: Ceder, G
EM: gceder@mit.edu
AF: MIT, 77 Massachusetts Ave, Cambridge, MA 02139-4307 United States
AU: Morgan, D
EM: ddmorgan@wisc.edu
AF: University of Wisconsin - Madison, 244 Materials Science & Engineering 1509 University Avenue, Madison, WI 53706-1595 United States
AB: One of the most abundant phases in the lower mantle is believed to be rocksalt magnesiowstite (Mg,Fe)O with approximately 20% Fe. At ambient conditions, the Fe²⁺ ion in (Mg,Fe)O is in high-spin configuration. Recently, experiments have shown that the Fe²⁺ ion in (Mg,Fe)O undergoes a pressure-induced high-spin to low-spin transition which could possibly influence lower mantle dynamics. We present ab initio calculations of the rocksalt (Mg,Fe)O spin state as a function of pressure and composition. We find that the spin-transition pressure increases with increasing Fe content, consistent with present experimental evidence. We demonstrate that this can be explained through a simple size argument, but only after differences in elastic properties are taken into account.
DE: 3924 High-pressure behavior
DE: 5109 Magnetic and electrical properties (0925)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005