A SIMPLIFIED STOCHASTIC DESCRIPTION FOR THE A-2 SURFACE-REACTION INCLUDING A-DIFFUSION(B)

We introduce a simplified stochastic model for the A+B-2 surface react ion with diffusion of the monomer particle. We use a stochastic descri ption which consists only of an autonomous differential equation syste m with four variables (the coverage of A and B and the corresponding p airs). The solution of this system is a straightforward process. We co mpare the values of the phase transition points with a much more compl ex stochastic ansatz which has been introduced earlier [Mai, Kuzovkov, and von Niessen, J. Chem; Phys. 100, 6073 (1994)]. We find good agree ment in the prediction of the first-order phase transition with the co mplete treatment. The ansatz also gives the second-order transition, b ut the results are not quantitative in the neighborhood of the second- order phase transition.