REVERSIBLE TRAPPING ON A CUBIC LATTICE - COMPARISON OF THEORY AND SIMULATIONS

Simulations of the kinetics of the reversible diffusion-influenced reaction A + B reversible AB on a cubic lattice, with initial conditions [A] = [B], [AB] = 0, are compared with the predictions of two approximate theoretical formalisms. The first involves a simple rate equation with rate coefficients that are proportional to the time-dependent rate coefficient for an irreversible reaction. The second, which is based on a superposition approximation, contains a rate coefficient that explicitly depends on the bulk concentrations. Both reduce to the Smoluchowski approach in the irreversible limit. The results obtained using the modified rate equation formalism are exact at short times, but tend to approach equilibrium too rapidly. The predictions of the computationally more demanding superposition formalism agree remarkably well with the simulations for all times for the range of parameters examined.