Mean-field analysis and Monte Carlo study of an interacting two-species reaction model

We study the phase diagram and critical behavior of an interacting one-dimensional two-species monomer-monomer catalytic surface reaction model with a reactive phase as well as two equivalent adsorbing phases where one of the species saturates the system. The model depends on two parameters: the relative adsorption rates of the two species and a repulsive interaction between like neighbors. A mean-field analysis including correlations up to triplets of sites fails to reproduce the phase diagram found by Monte Carlo simulations. The three phases coexist at a bicritical point whose critical behavior is described by the even branching annihilating random-walk universality class. This work confirms the hypothesis that the conservation modulo 2 of the domain walls under the dynamics at the bicritical point is the essential feature in producing critical behavior different from directed percolation. The interfacial fluctuations show the same universal behavior seen at the bicritical point in a three-species model, supporting the conjecture that these fluctuations are an additional universal characteristic of the model. © 1997 The American Physical Society