RATE-PROCESSES ON MODERATELY SMOOTH SURFACES

To describe the effect of lateral interactions between adsorbed particles on the kinetics of rate processes on uniform surfaces, the lattice-gas models are usually employed. Traditionally, these models are based on the idea that the equilibrium positions of adsorbed particles are fixed rigidly on the surface. This assumption may be incorrect in many real systems (including such traditional systems as CO or hydrogen on different metals), where the activation energy for surface diffusion is not very high (or is low) compared to lateral interactions between nearest-neighbor adsorbed particles (i.e., where the surface is smooth). In the present paper, a general theory is developed to take into account the influence of shifts of equilibrium position of adparticles on the kinetics of various rate processes on solid surfaces. The theory is applicable to the case when the activation energy for surface diffusion exceeds lateral interactions between adparticles. The shifts of equilibrium positions are shown to result in significant changes in the rate constants of various processes. The effect of shifts on the coverage dependence of the apparent Arrhenius parameters for desorption, thermal desorption spectra, and the coverage dependence of the chemical diffusion coefficient is also demonstrated in detail.