The effect of adsorbate-induced surface reconstruction on the motion of adsorbed particles was analyzed by means of Monte Carlo modelling. The reconstruction was assumed to be the order–disorder phase transition that was described by the two-position model introduced by A.V.Myshlyavtsev et alia (1990). The lattice gas model was used to mimic the hydrogen adsorption on the (001) face of tungsten [H/W(001)], which presents a c(2 x 2) structure below the critical temperature, Tc. The phase diagram of the real system was reproduced only at low coverages (0.25). One of the principal features of the model was that the critical temperature could either increase or decrease with coverage, depending on the relation of the parameters which describe the system. In addition, different ordered phases, such as c(2 x 2) and (2 x 1) could be present according to the characteristics of the metal–metal, adsorbate–adsorbate and adsorbate–metal interactions. Utilizing Monte Carlo simulations it was characterized how the behaviour of the chemical, D, the jump, DJ, and the tracer, D*, diffusion coefficients depend on the different ordered phases predicted by the model. In order to calculate the chemical diffusion coefficient, the fluctuation and Kubo–Green methods were applied. Surface diffusion was strongly anisotropic for the (2 x 1) ordered phase, indicating that it was facilitated in one direction and reduced in another.

The Influence of Surface Reconstruction on the Collective Motion of Adsorbed Atoms. F.Nieto, C.Uebing, V.Pereyra: Surface Science, 1998, 416[1-2], 152-66