Cellular automata approach to dissociative adsorption of diatomic molecules on a substrate with reconstruction

Abstract

A cellular automaton model is applied to the chemisorption of a diatomic molecule on a substrate consisting of active and inert component sites and performing a surface reconstruction. In the absence of surface migration or desorption of the adatoms the simulation shows a sharp transition between the unreconstructed surface phase and the induced surface reconstruction (first-order transition). The effect of desorption and migration is to soften this transition, becoming second order. When the presence of immobile impurities is taken into account the results show that the saturation coverage decreases almost linearly in the interval 0 < c < 0.9, where c is the impurity fraction. The effect of the statistical isolation of active sites is to make the relationship nonlinear for high values of the impurities fraction. The results compare well with the predictions of the approximation scheme used by Nord, R. S., and Evans, J. W., 1985, J. chem. Phys., 82, 2795.