Atomic transport property of Fe–O liquid alloys in the Earth’s outer core P, T condition

The self-diffusion and tracer diffusion coefficients and viscosity of non-magnetic liquid Fe–O alloys were determined at 100–350 GPa and 4000–8000 K on the basis of the ab initio molecular dynamics simulation method. Those of pure liquid iron are found to be consistent with the results of former studies. We confirmed that the self-diffusivity of Fe monotonically increases with increasing oxygen fraction. Meanwhile, the viscosity monotonically decreases with increasing oxygen fraction. On the other hand, the depth dependence of diffusivities and viscosity in the outer core are not great along the geotherm because pressure and temperature conversely affect the transport coefficients. The calculated diffusivity suggests that an O-rich stratified layer with a thickness of ∼70 km could be produced at the uppermost layer of the outer core if the layer was created from the diffusion of O from the mantle.