The role of the diffusion process in bimolecular reactions with neighborhood

We performed stochastic and deterministic calculations to study simple bimolecular chemical kinetics with a neighborhood, necessary for solid‐state and viscous medium reactions. Regarding the standard deterministic method using ordinary differential equations (ODEs) to describe a bimolecular reaction with the neighborhood, we established a comparison that indicates, in this method, an implicit diffusion process. For example, the reaction is processed in a homogeneous medium, differently from the stochastic method without diffusion. The two methods coincide at the thermodynamic limit (containing little relative fluctuation) when added with the explicit diffusion process on the stochastic model. The irreversible reaction without diffusion was emulated using the ODEs of a reversible reaction, and the inherent residual concentration of the reactions with low or no diffusion occurring in solids or strong viscous media was obtained from pseudochemical equilibrium.