Spontaneous symmetry breaking in a NO + CO surface reaction model

A simple lattice gas model for the catalytic CO + NO → CO2 + 12 N2 surface reaction is studied by means of a model involving a stochastic cluster approximation. The cluster approximation on an infinite square lattice gives a reactive interval from a second-order phase transition at y1 = 0.171 to a first-order phase transition at y2 = 0.319. The subdivision of the lattice into two chequerboard-like sublattices leads to a third phase transition at yCO = 0.227 where the reactive interval ends. This point is the left-hand limit of the domain of spontaneous symmetry breaking where a phase transition from dynamical disorder to static order occurs.