KINETIC PHASE-TRANSITION OF THE DIMER-DIMER SURFACE-REACTION MODEL

The dimer-dimer (DD) reaction model 1/2A(2)+B-2-->AB(2) is studied by means of Monte Carlo simulation and mean field theory based on the law of mass action, site approximation, and pair approximation. We find t hat both site and pair approximation can well reproduce the phase diag rams of the DD model. This fact implies that correlation effects are n ot so important in the vicinity of the first-order phase transition ch aracteristic of the DD model. A variant of the DD model, which account s for the recombination of the intermediate product C, is also studied . We find that C+ C reaction does not change the qualitative critical behavior of the DD model.