The effects of phase transitions, surface diffusion, and defects on surface catalyzed reactions: Fluctuations and oscillations

Abstract

Kinetic oscillations in catalytic reactions are often attributed either to attractive absorbate-absorbate interactions between adatoms or to required vacant sites for chemical reaction and are usually described by ordinary differential equations. These mechanisms are examined as possible causes for oscillations in surface reactions using Monte Carlo simulations. Self-sustained oscillations driven by a phase transition on the catalyst surface are found. It is shown that spatial inhomogeneity of the surface controls the existence of oscillations which therefore cannot be modeled using ordinary differential equations. The problem of synchronization of numerous oscillators on the surface is investigated. In particular, the influence of adatom migration and surface defects on Hopf bifurcation is examined. It is demonstrated that sites on surface with strong binding energy result in more chaotic oscillations whose amplitude decreases. The influence of concentration and distribution of defects on the kinetic oscillations is discussed. © 1990 American Institute of Physics.