We report molecular dynamics simulation results for two-component fluidmixtures of Gaussian-core particles, focusing on how tracer diffusivities andstatic pair correlations depend on temperature, particle concentration, andcomposition. At low particle concentrations, these systems behave like simpleatomic mixtures. However, for intermediate concentrations, the single-particledynamics of the two species largely decouple, giving rise to the followinganomalous trends. Increasing either the concentration of the fluid (at fixedcomposition) or the mole fraction of the larger particles (at fixed particleconcentration) enhances the tracer diffusivity of the larger particles, butdecreases that of the smaller particles. In fact, at sufficiently high particleconcentrations, the larger particles exhibit higher mobility than the smallerparticles. Each of these dynamic behaviors is accompanied by a correspondingstructural trend that characterizes how either concentration or compositionaffects the strength of the static pair correlations. Specifically, the dynamictrends observed here are consistent with a single empirical scaling law thatrelates an appropriately normalized tracer diffusivity to its pair-correlationcontribution to the excess entropy.
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