  We study the phase diagram and critical behavior of a one dimensional three
species monomer-monomer surface reaction model. Static Monte Carlo simulations
show a phase diagram consisting of a reactive steady state bordered by three
equivalent unreactive phases where the surface is saturated with one monomer
species. The transitions from the reactive to saturated phases are all
continuous, while the transitions between poisoned phases are first-order, with
bicritical points where the reactive phase meets two poisoned phases. A
mean-field cluster analysis predicts all of the qualitative features of the
phase diagram only when correlations up to triplets of adjacent sites are
included. Dynamic Monte Carlo simulations show that the transition from the
reactive to a saturated phase show critical behavior in the directed
percolation universality class, while the bicritical point shows critical
behavior in the even branching annihilating random walk class. The crossover
from bicritical to critical behavior is also studied.
