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The high-temperature elasticity of MgSiO3 post-perovskite

2007; American Geophysical Union; Linguagem: Inglês

10.1029/174gm09

2328-8779

Stephen Stackhouse, John P. Brodholt,

Geological and Geochemical Analysis

The elastic properties of pure MgSiO 3 post-perovskite have been determined at lower mantle temperatures and pressures using density functional theory based molecular dynamics simulations. Calculated isotropic seismic wave velocities and densities for a pyrolitic mantle composition, based on these values and high temperature elastic properties for magnesiowustite and calcium perovskite from other theoretical studies, match PREM, to within 1 percent, assuming a temperature of 2900 K. ∂lnV s /∂lnV p is found to be about 2.2 ± 0.1, in better agreement with observations than our previously calculated value. The general observation of horizontally polarised shear-waves travelling about one percent faster, on average, than vertically polarised shear-waves in the lowermost mantle, is found to be possible assuming the (010) slip plane, suggested from experimental studies, and about fifty percent crystal alignment. Comparison of bulk and shear moduli and isotopic wave velocities with those calculated from lattice dynamics based calculations [Wentzcovitch et al., 2006] indicates that they are in accord (within a few percent) up to 2500 K, but diverge significantly at higher temperatures. In contrast, the elastic anisotropy of the studies differs at all temperatures. Possible reasons for these discrepancies are discussed in detail.