HR: 11:02h
AN: MR22A-04    [Abstracts]
TI: Fe Spin Crossover in Lower Mantle Materials: A First-Principles Study
AU: * Bengtson, A
EM: akberta@wisc.edu
AF: University of Wisconsin - Madison, 1509 University Ave, Materials Science and Engineering, Madison, WI 53706, United States
AU: Persson, K
EM: kpersson@MIT.EDU
AF: Massachusetts Institute of Technology, Department of Materials Science and Engineering, Room 13-5061, Cambridge, MA 02139, United States
AU: Morgan, D
EM: ddmorgan@wisc.edu
AF: University of Wisconsin - Madison, 1509 University Ave, Materials Science and Engineering, Madison, WI 53706, United States
AB: Ab initio calculations of the zero-temperature composition dependent Fe high- to low-spin transition in (Mg_1-x,Fe_x)SiO₃ perovskite and (Mg_1-x,Fe_x)O ferropericlase are presented and comparisons are made between the two structures. Opposite trends in spin crossover dependence on composition are obtained. The possible role of high, intermediate, and low spin states is also discussed. We explain the large spread in computational Fe spin transition pressure in perovskite seen in the literature by differences in calculation parameters such as exchange correlation type, exchange correlation parametrization, pseudopotential choice, and correlation corrections (LDA+U). We also find the spin transition pressure to be very sensitive to materials systems parameters such as structural relaxation (especially for high Fe content), composition, local chemical ordering, valence, and magnetic ordering. Our results indicate that there needs to be consistency in both calculation and materials systems parameters when comparing calculation results and when comparing calculations to experiments.
DE: 3914 Electrical properties
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3999 General or miscellaneous
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting