Saturation and negative temperature coefficient of electrical resistivity in liquid iron-sulfur alloys at high densities from first principles calculations

TL;DR

This study uses first-principles calculations to explore how liquid iron-sulfur alloys' electrical resistivity behaves under high-pressure planetary core conditions, revealing saturation effects and a sign change in temperature dependence.

Contribution

It provides new insights into the electronic transport properties of liquid Fe-S alloys at core-like conditions, highlighting the effects of saturation and negative temperature coefficients from first-principles.

Findings

Resistivity saturation occurs due to temperature, compression, and chemistry effects.

At high compression and sulfur levels, the Ioffe-Regel limit is reached.

The temperature coefficient of resistivity becomes negative due to decreased d-density of states.

Abstract

We report results on electronic transport properties of liquid Fe-S alloys at conditions of planetary cores, computed by first-principle techniques in the Kubo-Greenwood formalism. We describe a combined effect of resistivity saturation due to temperature, compression, and chemistry by comparing the electron mean free path from the Drude response of optical conductivity to the mean interatomic distance. At high compression and high sulfur concentration the Ioffe-Regel condition is satisfied, and the temperature coefficient of resistivity changes sign from positive to negative. We show that this happens due to a decrease of the $d$-density of states at the Fermi level in response to thermal broadening.