Adsorption, desorption and diffusion of extended objects on a square lattice

Kinetics of the adsorption-desorption process with diffusional relaxation is studied by Monte-Carlo simulations on a square lattice. At each Monte-Carlo step three independent processes proceeding in parallel are attempted: adsorption, desorption and diffusion. The time is measured by the number of adsorption attempts per lattice site and the kinetics of the process is governed by the ratios of desorption to adsorption rate and diffusion to adsorption rate. The process is reversible and after long enough time the system reaches an equilibrium state. For a given desorption/adsorption rate ratio equilibrium coverage is not affected by the diffusion rate, while the diffusion fastens the approach to the equilibrium state. These simulations could also be useful for explanation of the densification process in granular materials. (C) 2003 Elsevier B.V. All rights reserved.