ON THE INFLUENCE OF REACTANTS INDUCED SURFACE TRANSFORMATIONS IN THE BEHAVIOR OF A HETEROGENEOUSLY CATALYZED DIMER-MONOMER REACTION MODEL

A surface reaction model for the catalyzed reaction A +(1/2)B-2-->AB i s studied by means of Monte Carlo simulations. Motivated by experiment s on the catalytic oxidation of CO on certain Pt surfaces; i.e., A=CO, B-2=O-2, and AB=CO2; it is assumed that the catalyst surface undergoe s reactant's induced reversible phase transitions (RIRPT's) between tw o different structures, i.e., a stable (reconstructed) phase in the lo w (high) A-coverage regime. Also the sticking coefficient of B-2-speci es depends on the surface structure, being negligible in the stable ph ase. Two cases are studied in detail depending on whether the RIRPT's involve the whole surface and are due to the average coverage of the s ample or, on the other hand, they are restricted to small patches of t he surface and are driven by the local coverage. For the case of globa l RIRPT's, the reactive regime of the system exhibits self-sustained o scillatory behavior. However, considering local RIRPT's oscillations a re observed in finite samples but it is shown that they will vanish in the thermodynamic limit. (C) 1998 American Institute of Physics. [S00 21-9606(98)50340-6].