HR: 0830h
AN: V51A-08    [Abstracts]
TI: First Principles Calculations of Point Defects in Major Mantle Minerals
AU: * Karki, B
EM: karki@bit.csc.lsu.edu
AF: Louisiana State University, 283 Coates Hall, Baton Rouge, LA 70803 United States
AB: First-principles calculations within the local density and pseudopotential approximations are performed to investigate the effects of pressure on the energetics and structural behavior of charged vacancy defects in MgO and MgSiO3 perovskite. The simulations are performed for a supercell containing a couple of hundreds of atoms with their positions being fully optimized. In particular, the formation and migration energies of cation and anion vacancies are shown to substantially increase over the pressure regime of Earth's mantle. Our results thus suggest that pressure should suppress intrinsic diffusion mediated by ionic vacancies in these two major mantle minerals over the mantle pressure regime. The calculated three-dimensional datasets for atomic displacements and electron charge density are explored in details using an interactive visualization system. Although the atomic and electronic structures are mostly distorted in the close vicinity of the defects (i.e., in the region covering up to the nearest and next-nearest atoms), the effects are not negligible at farther distances.
DE: 1025 Composition of the mantle
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 3902 Creep and deformation
DE: 3904 Defects
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly