A PHENOMENOLOGICAL MONTE CARLO SIMULATION OF A TWO-STEP DIMER/MONOMER SURFACE REACTION

Abstract

In the past few years stochastic models have been extensively used to describe the adsorption and reaction of molecules on metallic surfaces. One such model was due to Ziff, Gulari and Barshad (ZGB) which despite its simplicity was able to capture some important features of surface reactions such as steady state, phase transition and surface poisoning. However, in all the contributions that used the ZGB model the reactants were assumed to occupy similar sites on the metallic surface. The intent of this contribution is to investigate a more complicated two-step monomer/dimer model reaction of the form A2 + B → (AB)ads + B → A2B in which the reacting species adsorb on distinct sites on the metallic surface, e.g. four-fold hollow- and bridge-bonding. In this context, it was found that the lack of correlation between surface concentrations leads to a dramatic breakdown of the site approximation which did not occur when only equivalent surface sites are used.