Dynamic correlation effect in reversible diffusion-influenced reactions: Brownian dynamics simulation in three dimensions

A Brownian dynamics (BD) simulation for a pseudo-first-order diffusion-influenced reversible association-dissociation reaction of a target system in three dimensions with spherical symmetry is presented. The exact Green function for a reversible geminate dissociation that we obtained recently is utilized in the simulation. We compare the results of simulation with two successful theoretical predictions, the enhanced version of the superposition approximation approach (SA) and the more rigorous kinetic theoretical approach (KT). The KT predicts the correct power law behavior of similar to t(-3/2) with a slightly higher amplitude in the long-time region, but it is in good agreement with the BD result in the transient region. On the other hand, a faster relaxation is observed in the transient region for the SA, but the correct power law behavior with numerically exact amplitude is predicted for the exact target system. An interesting interplay between the mobility of the system and the dynamic correlation effect incorporated with many-body problems is also revealed. (C) 1999 American Institute of Physics. [S0021-9606(99)51227-0].