Electrical and thermal transport properties of Fe–Ni based ternary alloys in the earth's inner core: An ab initio study

Abstract

Besides iron, the Earth's core also contains 5–10% of nickel and several light elements such as H, C, N, O, Si and S. Fe-Ni alloys have been considered as the host material with 10% Ni. The impurity atoms which are comprised of the light elements have been incorporated at different concentrations in the host alloy, giving rise to ternary alloys. All these systems have been subjected to compression at pressures similar to that in the inner core of the Earth. The atomic concentration of the impurities has been varied from 2.5% to 50%. The formation enthalpies suggest that these ternary alloys are energetically favorable. The impurity resistivity is calculated using the Kubo-Greenwood formula. At approximately ~30% of atomic concentration of impurities, the electrical resistivities start to saturate. For lesser percentage of hydrogen, the impurity resistivity is in the same range as that of the rest. But once the concentration of hydrogen increases, the impurity resistivity becomes very high. Generally, the resistivities are seen to plummet with increasing pressure. Using the Wiedemann-Franz law, the thermal conductivities were also determined from the calculated electrical resistivities for both varying concentration and pressure. On compression, the thermal conductivities increased by approximately 5% in the inner core pressure range.