KINETIC PHASE-TRANSITIONS IN DIMER-DIMER SURFACE-REACTION MODELS STUDIED BY MEANS OF MEAN-FIELD AND MONTE-CARLO METHODS

Dimer-dimer surface reaction models inspired in the catalytic oxidation of hydrogen on transition metal surfaces - which may apply to generic bimolecular reactions of the type (1/2)A2 + B2 --> B2A - are studied by means of a mean-field approach and Monte Carlo simulations. The models exhibit irreversible (kinetic) phase transitions (IPT) from a reactive stationary regime with B2A production to poisoned states where the surface becomes saturated by the reactants. The critical points at which IPTs take place are determined. The critical behavior of relevant quantities, such as the rate of B2A production and the coverage with the reactants, is studied and the corresponding critical exponents are evaluated. Good qualitative agreement is found when comparing mean-field and Monte Carlo results.