Kinetic and equilibrium competition of gases during mixture adsorption on planar surfaces

We present results of a Kinetic Monte Carlo investigation of the adsorption dynamics of a binary mixture of gases on a planar surface, with a focus on the role that molecular interactions play during equilibration. We show how increasing the strength of molecular interactions enhances the weaker species overshoot, a phenomenon driven by the faster adsorption rate of this species. Snapshots of the adsorbed mixture configurations as a function of time allow us to follow in detail the evolution of the system towards equilibrium, including the complete displacement of one species by the other. Clustering effects due to both molecular interactions and differences in the adsorption/desorption rates determine how the competition between the species for empty spaces on the surface takes place, leading to the final equilibrium composition. We compare our results to some available experimental measurements of the adsorption kinetics of argon/methane and nitrogen/methane mixtures of graphite.