Computer simulation methods for diffusion-controlled reactions

Abstract

We discuss various computer simulation techniques for the study of nonequilibrium diffusion‐controlled reactions. These include: the minimal process method which simulates a master equation describing the process; the ‘‘direct’’ method which simulates the actual motion and reactions of the particles; and a new simulation method which we term the renormalized reaction‐cells method (RRC). The RRC is a variation of the minimal process method which makes use of some scaling ideas. The reaction cells of the minimal process method are renormalized as the concentration of the reactants in the system decreases. The probabilities for diffusion and for reaction, as well as the time increase associated with the processing of a cell, are renormalized in a corresponding fashion. The shortcomings and strengths of each simulation method are pointed out. Several examples of diffusion‐controlled reactions are simulated by the direct method and by the RRC method. It is shown that the RRC is superior to the other simulation methods in many respects.