Ab Initio Determination on Diffusion Coefficient and Viscosity of FeNi Fluid Under Earth’s Core Condition

Abstract

The Earth’s outer core is mainly composed of Fe and Ni. The compositional stratification and geodynamo of the Earth’s core are closely correlated with the transport properties of the fluid in the Earth core. We selected the typical FeNi fluid, and systemically calculated its diffusion coefficient and viscosity under Earth’s core condition by quantum molecular dynamics simulation. The diffusion coefficients and viscosity are almost constant along the core adiabatic curve. The self-diffusion coefficients of Ni along the core adiabatic range from 8.37\(\times\)10−9 m2s−1 to 8.87\(\times\)10−9 m2s−1. The diffusion coefficient increases with temperature increase, while viscosity decrease with temperature increase. The calculations on the transport properties suggest that the Ni impurities have a negligible effect on the diffusion coefficient and viscosity of Earth’s core. Combining the self-diffusion coefficient of Ni and the diffusion equation, the thickness of compositional stratification at the top of the core is 138.5 km.