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

Abstract

The ZGB model (Ziff–Gulari–Barshad, Phys. Rev. Lett. 56 (1986) 2553) for the catalytic oxidation of carbon monoxide has a single parameter given by the normalized partial pressure of CO molecules ( P CO). For P CO⩾ P CO Coex≃0.52583 the surface of the catalyst becomes irreversibly covered by CO molecules and the system cannot escape 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-order 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 accurate evaluation of the upper spinodal point given by P CO Usp≃0.52675(5). This figure is in excellent agreement with extensive simulations performed using the constant coverage ensemble.