The influence of both pairwise and 3-particle interactions upon the mobility of adsorbed particles diffusing on a lattice with triangular symmetry was studied. Two different techniques were used for describing the surface diffusion phenomenon. On one hand, explicit expressions for the chemical and jump diffusion coefficients were calculated by using the real-space renormalization group approach. A number of real-space renormalization group transformations with blocks of different sizes and symmetries were investigated. In particular, it was shown that the precision of the method depended strongly not only upon the number of sites in the real-space renormalization group blocks but also upon their composition and structure. On the other hand, Monte Carlo methods were used to simulate the process of particle migration. Using both methods, adsorption isotherms for different temperatures and the coverage dependences for the thermodynamic factor and the chemical diffusion coefficient were calculated. The behavior of the above quantities was compared for cases where the ad-particles interacted via only either pairwise or 3-particle interactions. Despite the fact that both methods constituted very different approaches, the correspondence of numerical data with analytical results was surprisingly good. Therefore, it was concluded that the real-space renormalization group method could be successfully applied to lattice gas systems in order to characterize the thermodynamic and kinetic properties of strongly interacting adsorbates.

Diffusion of Particles Adsorbed on a Triangular Lattice - Pairwise and Three-Particle Interactions. A.A.Tarasenko, F.Nieto, L.Jastrabík, C.Uebing: Surface Science, 2003, 536[1-3], 1-14