  Molecular dynamics simulations and a stochastic Fokker-Planck equation based
approach are used to illuminate how position-dependent solvent mobility near
one or more tracer particle(s) is affected when tracer-solvent interactions are
rationally modified to affect corresponding solvation structure. For tracers in
a dense hard-sphere fluid, we compare two types of tracer-solvent interactions:
(1) a hard-sphere-like interaction; and (2) a soft repulsion extending beyond
the hard core designed via statistical mechanical theory to enhance tracer
mobility at infinite dilution by suppressing coordination-shell structure
(Carmer et al., Soft Matter 8 (2011)). For the latter case, we show that the
mobility of surrounding solvent particles is also increased by addition of the
soft repulsive interaction, which helps to rationalize the mechanism underlying
the tracer's enhanced diffusivity. However, if multiple tracer surfaces are in
closer proximity (as at higher tracer concentrations), similar interactions
that disrupt local solvation structure instead suppress the position-dependent
solvent dynamics.
