Position-dependent and pair diffusivity profiles from steady-state solutions of color reaction-counterdiffusion problems

We show how the steady-state solution of the Smoluchowski (Fokker-Planck) equation for a color reaction-counterdiffusion problem, together with equilibrium trajectory information (e.g., from molecular simulations or confocal microscopy experiments), can be used to determine position-dependent or pair diffusivity profiles for condensed phases directly without the need for Bayesian inference, likelihood maximization, or the analysis of time-dependent data.