Fractals and patterns in catalysis

We have carried out Monte Carlo simulations to demonstrate pattern formation (trigger waves) in a model for the catalysis of the oxidation of CO on a Pt surface. We use a modified version of the model proposed by Ziff et al. (Phys. Rev. Lett. 50 (1986) 2553). We study the evolution of the trigger wave, i.e. the reaction front, as a function of partial pressure of CO as well as diffusion of CO. We find that the fluctuations in the interface follow the KPZ equation; that is, the reaction front is a self-affine fractal surface. We find a cross-over region for low speeds of the propagating wavefronts where exact KPZ exponents are not obtained.