A general stochastic model for the description of surface reaction systems

In this paper we introduce a stochastic ansatz which can be used to model surface reaction systems. The systems may include mono- and bimolecular steps (i.e. adsorption, desorption, reaction and diffusion steps). We take advantage of the Markovian behaviour of these systems by using master equations for their description. The resulting infinite chain of equation is truncated at a certain level: In a small lattice region we solve the exact lattice equations and connect their solution to continuous functions which represent the behaviour of the system for large distances from a reference point. The stochastic ansatz is used to model different surface reaction systems such as the oxidation of CO on a Pt surface and on a Pt/Sn alloy. Also the formation of NH3 is discussed.