Class of Cellular Automata for the Formation of Surface Aggregates

A class of cellular automata is constructed on the basis of a set of simple rules: virtual particles obeying a full exclusion principle are subject to probabilistic dynamics with nonlocal (attractive and repulsive) interactions, and with momentum transfer memory effects. Boundary conditions can be periodic or can be set to simulate open systems, with various geometries. This model system possesses the essential elements to simulate the formation of surface aggregates. A specific application is presented for the formation and the dynamics of islands of hydroxyl groups in the catalytic reduction of NO on a Pt surface. The comparison between the simulation results and the experimental observations by Field Ion Microscopy suggests possible mechanisms for the so-far unexplained formation and dynamics of hydroxyl islands during the NO reduction processes.