THE CRITICAL-BEHAVIOR OF DIMER DIMER SURFACE-REACTION MODELS - MONTE-CARLO AND FINITE-SIZE SCALING INVESTIGATION

Two models based upon the well-known mechanism for the oxidation of hydrogen on transition metal surfaces, which may also apply to generic dimer-dimer surface reaction processes of the type (1/2) A2 + B2 --> B2A, are proposed and studied on the square lattice of side L (L less-than-or-equal-to 600) by means of Monte Carlo simulations and finite-size analysis. Both models exhibit irreversible (kinetic) phase transitions (IPT) from a reactive state with sustained production of B2A molecules to off-equilibrium surface poisoned states with the reactants, i.e., without production. The location of the critical points at which the IPTs take place in the L = infinity limit is determined by means of a finite-size scaling analysis. Also, it is shown that at criticality some relevant quantities, such as the rate of B2A production and the coverage with the reactants, exhibit simple power-law behavior, which allow us to determine the corresponding critical exponents.