Electrical resistivity of Fe-C and Fe-Si alloy at high pressure and the light element effects on Earth's core

The thermal conductivity of iron alloys is one of the key parameters of Earth's core which controls the heat conduction, thermal evolution, and geodynamics of the deep interior of Earth. We report the electrical resistivity of pure iron and a set of Fe-C and Fe-Si alloys at high pressures based on the measurement with van der Pauw method in diamond anvil cell. The results show significant changes in the electrical resistivity of these iron alloys which are attributed to structural and electronic transitions at high pressures. These changes indicate that the electrical and thermal conductivity of Earth's core is largely influenced by structures of candidate Fe alloys. Then the results are applied to understand the thermal transport behavior of Earth's core. Using Wiedemann-Franz law, the electrical resistivity is transformed to thermal conductivity. We compared the thermal conductivity of Fe alloys at the outer and inner core condition which shows divergence resulted from different identities and levels of light element alloying. Among the light elements investigated, carbon shows the strongest alloying effect which is capable of greatly decreasing the thermal conductivity of iron. In our presentation, we also discuss how the thermal conductivity of Earth's core affects our understanding of thermal evolution and geodynamics of our planet.