HR: 1340h
AN: MR23A-0189    [Abstracts]
TI: Elasticity and stability of FeSi at high pressures
AU: * Wentzcovtich, R
EM: wentzcov@cems.umn.edu
AF: University of Minnesota, Dept. of Chemical Engineering and Materials Science, 421 Washington Ave. SE, Minneapolis, MN 55455 United States
AU: Caracas, R
EM: r.caracas@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory, 5251 Broad Branch Rd., N.W., Washington, DC 20015 United States
AB: We have used both the Local Density Approximation (LDA) and the Generalized Gradient Approximation (GGA) to Density Functional Theory (DFT) to invetigate the structural and elastic behavior of FeSi throughout Earth's lower mantle pressure regime. At lowermost mantle pressures, FeSi is in the B2 (CsCl-type) structure, and has a metallic character. The B20-B2 transition occurs between 30-40 GPa in these static calculations and is associated with a density increase of 0.35 g/cm$^3$ (\~4.8%). FeSi is heavier than the mantle and lighter than the core. For this reason and because it is a possible product of the reaction between liquid Fe and MgSiO$_3$, it may accumulate at the base of the mantle, in the D" layer. Throughout the lower mantle regime, its velocities are lower than PREM's by 1.5-2 km/s for V$_p$ and 0.6-0.9 km/s for V$_s$. If present in the D'' layer, by up to a few percents in volume, the B2 phase of FeSi will contribute to decrease both V$_p$ and V$_s$.
DE: 3620 Crystal chemistry
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting