Monte Carlo simulations of the short time dynamics of a first-order irreversible phase transition

The ZGB model (Ziff-Gulari-Barshad, Phys. Rev. Lett. 56 (1986) 2553) for th e catalytic oxidation of carbon monoxide has a single parameter given by th e normalized partial pressure of CO molecules (P-CO). For P-CO greater than or equal to P-CO(Coex) similar or equal to 0.52583 the surface of the cata lyst becomes irreversibly covered by CO molecules and the system cannot esc ape from this state. However, for P-CO slightly below P-CO(Coex) the system reaches an active stationary state. So, just at P-CO(Coex) a sharp first-o rder irreversible phase transition is observed. It is shown that a study of the short time dynamics of the ZGB model allows to obtain a fairly accurat e evaluation of the upper spinodal point given by P-CO(Usp) similar or equa l to 0.52675(5). This figure is in excellent agreement with extensive simul ations performed using the constant coverage ensemble. (C) 2001 Elsevier Sc ience B.V. All rights reserved.