Thermodynamics of Spin Transitions in the Lower Mantle

HR: 17:45h
AN: MR14A-08 [Abstracts]
TI: Thermodynamics of Spin Transitions in the Lower Mantle
AU: * Morgan, D
EM: ddmorgan@wisc.edu
AF: University Of Wisconsin - Madison, 244 MSE, 1509 University Ave, Madison, WI 53706 United States
AU: Persson, K
EM: kpersson@mit.edu
AF: Massachusetts Institute of Technology, 13-4057, 77 Massachusetts Ave, Boston, MA 02139 United States
AU: Berta, A
EM: akberta@wisc.edu
AF: University Of Wisconsin - Madison, 244 MSE, 1509 University Ave, Madison, WI 53706 United States
AU: Ceder, G
EM: gceder@mit.edu
AF: Massachusetts Institute of Technology, 13-4057, 77 Massachusetts Ave, Boston, MA 02139 United States
AB: Recent experiments have confirmation spin transitions in Fe in both the rocksalt magnesiow《tite (Mg,Fe)O and perovskite (Mg,Fe)SiO₃ phases at lower mantle pressures. The spin-transitions have potentially profound implications for the materials properties of the lower mantle. However, the coupling of thermodynamic temperature effects and the spin transition is still poorly understood. In this talk we present an ab initio based thermodynamic model for Fe spin transitions in lower mantle phases. We build a free energy model which includes configurational, vibrational, magnetic, and electronic contributions. The resulting free energy expressions are used to construct a phase diagram for the lower mantle rocksalt phase which includes the impact of Fe spin transitions.
DE: 3924 High-pressure behavior
DE: 3939 Physical thermodynamics
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005