Transport properties for liquid silicon-oxygen-iron mixtures at Earth's core conditions

TL;DR

This study uses density functional theory to calculate the thermal and electrical conductivities of liquid silicon-oxygen-iron mixtures at Earth's core conditions, revealing higher values than previous estimates and implications for Earth's thermal and magnetic evolution.

Contribution

The paper provides new first-principles calculations of Earth's outer core liquid conductivities, significantly updating previous estimates with implications for geophysical models.

Findings

Thermal conductivities are 2-3 times higher than previous estimates.

Electrical conductivities are 2-3 times higher than previous estimates.

Results suggest faster cooling rates and higher radiogenic element levels in Earth's core.

Abstract

We report on the thermal and electrical conductivities of two liquid silicon-oxygen-iron mixtures (Fe$_{0.82}$Si$_{0.10}$O$_{0.08}$ and Fe$_{0.79}$Si$_{0.08}$O$_{0.13}$), representative of the composition of the Earth's outer core at the relevant pressure-temperature conditions, obtained from density functional theory calculations with the Kubo-Greenwood formulation. We find thermal conductivities $k$ =100 (160) W m$^{-1}$ K$^{-1}$, and electrical conductivities $\sigma = 1.1 (1.3) \times 10^6 \Omega^{-1}$ m$^{-1}$ at the top (bottom) of the outer core. These new values are between 2 and 3 times higher than previous estimates, and have profound implications for our understanding of the Earth's thermal history and the functioning of the Earth's magnetic field, including rapid cooling rate for the whole core or high level of radiogenic elements in the core. We also show results for a number of structural and dynamic properties of the mixtures, including the partial radial distribution functions, mean square displacements, viscosities and speeds of sound.