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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. Upon decreasing the electron correlation from the Mott insulating phase, the delocalization of electrons gives rise to an increasing attractive interatomic interaction, which is expected to introduce an additional friction, hence reducing the atomic diffusivity. Yet, our quantum molecular dynamics simulations find an intriguing enhancement of the diffusion coefficient induced by the emerging attractive force. We show that this counterintuitive phenomenon results from the reduction of the repulsive core and the suppression of the attractive tail by thermal fluctuations. The proposed scenario is corroborated by the Chapman-Enskog theory and classical molecular dynamics simulations on a standard liquid model based on the Morse potential. Our work not only provides a general mechanism of the attraction-facilitated diffusion enhancement in simple liquids, but also sheds new lights on the nontrivial effects of electron correlation on atomic dynamics.