High-Pressure Elasticity of Iron and Anisotropy of Earth's Inner Core

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Science  31 Mar 1995:
Vol. 267, Issue 5206, pp. 1972-1975
DOI: 10.1126/science.267.5206.1972


A first principles theoretical approach shows that, at the density of the inner core, both hexagonal [hexagonal close-packed (hcp)] and cubic [face-centered-cubic (fcc)] phases of iron are substantially elastically anisotropic. A forward model of the inner core based on the predicted elastic constants and the assumption that the inner core consists of a nearly perfectly aligned aggregate of hcp crystals shows good agreement with seismic travel time anomalies that have been attributed to inner core anisotropy. A cylindrically averaged aggregate of fcc crystals disagrees with the seismic observations.

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