Two universality classes of the Ziff-Gulari-Barshad model with CO desorption via time-dependent Monte Carlo simulations

Abstract

We study the behavior of the phase transitions of the Ziff-Gullari-Barshad (ZGB) model when CO molecules are adsorbed on a catalytic surface with a rate y and desorbed from the surface with a rate k. We employ largescale nonequilibrium Monte Carlo simulations along with an optimization technique based on the coefficient of determination, in order to obtain an overview of the phase transitions of the model in the whole spectrum of y and k (0 y 1 and 0 k 1) with precision y = k = 0.001. Successive refinements reveal a region of points belonging to the directed percolation universality class, whereas the exponents θ and β/ν obtained agree with those of this universality class. On the other hand, the effects of allowing the CO desorption from the lattice on the discontinuous phase transition point of the original ZGB model suggest the emergence of an Ising-like point previously predicted by Tomé and Dickman [Phys. Rev. E 47, 948 (1993)]. We show that such a point appears after a sequence of two lines of pseudocritical points which leads to a unique peak of the coefficient of determination curve in yc = 0.554 and kc = 0.064. In this point, the exponent θ agrees with the value found for the Ising model.