Enhancement of Atomic Diffusion due to Electron Delocalization in Fluid Metals

We present a general theory of atomic self-diffusion in the vicinity of a Mott metal-insulator transition in fluid metals. Starting from the Mott insulating phase, the delocalization of electrons gives rise to the emergence of attractive interatomic interaction, which, according to Einstein's relation, is expected to introduce an additional friction, hence reducing the atomic diffusivity. Yet, our quantum molecular dynamics simulations find an intriguing enhancement of the atomic diffusion facilitated by the emerging attractive forces. We demonstrate that this counterintuitive phenomenon results from a reduced effective repulsive core when the effect of the attractive tail is suppressed at high temperatures. The proposed scenario, which could account for diffusion enhancement in general simple liquids, is corroborated by the Chapman-Enskog theory and classical molecular dynamics simulations on an archetypal liquid model based on the Morse potential. Our work also sheds new lights on the nontrivial effects of electron correlation on atomic dynamics.