Constraints on the thermal evolution of Earth's core from ab initio calculated transport properties of FeNi liquids

Abstract

Earth's magnetic field is generated by the liquid outer core and sensitively depends on the thermal conductivity of the core. The dominant component of the Earth's core is Fe (∼85%) and Ni (∼10%). However, current estimates on FeNi liquids have not been previously tested at high pressures. In this paper, ab initio simulations were first applied to calculations of the thermal and electrical conductivities of FeNi liquids at Earth's outer core conditions. The thermal conductivity along the adiabatic curve for FeNi fluid ranges from 120.52 to 202.80 W/m/K, but pure Fe ranges from 125.07 to 216.18 W/m/K. The age of the inner core calculated with thermal conductivity of FeNi fluid is 0.019 Ga longer than pure Fe. Nickel effect on the age of the inner core is of the same order with the uncertainty of density jump and latent heat at the inner-core boundary. Furthermore, by analyzing the effective temperature gradient, the present thickness of thermal stratification calculated with thermal conductivity of FeNi liquid is 64.5 km thinner than that of pure Fe.