Symmetry-breaking and percolation transitions in a surface reaction model with superlattice ordering

A symmetry-breaking order-disorder transition of the Ising type is found in a nonequilibrium surface reaction model for CO oxidation incorporating sup erlattice ordering of adsorbed oxygen. We relate this transition to the per colation of superlattice domains of oxygen, and discuss the consequences fo r chemical diffusion of coadsorbed CO. The latter constitutes a new type of problem involving transport in disordered media.