Correlating Tracer Particle Diffusivity with Excess Entropy

Previous work has shown that bulk dynamics can be correlated with structural and thermodynamic properties of the system. We extend these findings to include the infinite-dilution diffusivity of a single tracer particle. Using computer simulations, we explore how tuning the tracer-solvent interactions affects the dynamics of the tracer. Optimizing the tracer particle two-body contribution to excess entropy results in significant increases in tracer particle diffusivity. Further gains in dynamics were observed when the partial molar excess entropy of the tracer was maximized. While the impact of these optimizations becomes much greater at higher densities, we show that as the particle size is increased there exists a maximum in the relative increase that can be obtained. The potentials obtained through this optimization routine were then approximated by two different types of interaction potentials we see in real systems: Yukawa and polymer brushes. Our simulations show that increases in diffusivity were comparable to the original optimized potentials.