Diffusion and desorption processes in ordered (2×2) lattice gas phase

We study two-dimensional lattice gas with interaction dependent rates of the particle diffusion and desorption. We run Monte Carlo dynamics and study decay of harmonic perturbation of the profile. In the close to equilibrium, long-wavelength limit dynamics separate into desorption process, independent of the perturbation wave vector k, and proportional to k2 collective diffusion. In most cases both processes can be analyzed separately. We show that in some highly ordered systems, like (2×2) ordered structure of repulsive square lattice gas, one process can change characteristics of the other. We observe that the diffusion coefficient becomes slower when the desorption process is more rapid. This effect is even more visible in higher temperatures. As a result the measured activation energy of the diffusion process can be changed by the presence of the rapid desorption and adsorption processes even when system is close to equilibrium.