Science. 2013 Oct 25;342(6157):466-8. doi: 10.1126/science.1243651. Epub 2013 Oct 10.

Strong premelting effect in the elastic properties of hcp-Fe under inner-core conditions.

Science (New York, N.Y.)

Benjamí Martorell, Lidunka Vocadlo, John Brodholt, Ian G Wood

PMID: 24114785 DOI: 10.1126/science.1243651

Abstract

The observed shear-wave velocity VS in Earth's core is much lower than expected from mineralogical models derived from both calculations and experiments. A number of explanations have been proposed, but none sufficiently explain the seismological observations. Using ab initio molecular dynamics simulations, we obtained the elastic properties of hexagonal close-packed iron (hcp-Fe) at 360 gigapascals up to its melting temperature Tm. We found that Fe shows a strong nonlinear shear weakening just before melting (when T/Tm > 0.96), with a corresponding reduction in VS. Because temperatures range from T/Tm = 1 at the inner-outer core boundary to T/Tm ≈ 0.99 at the center, this strong nonlinear effect on VS should occur in the inner core, providing a compelling explanation for the low VS observed.

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't