Monte Carlo simulations of the adsorption of potassium on a Cu(111) surface

Monte Carlo simulations of the adsorption of potassium on a Cu(111) surface at 80 K and coverages going from θ=0.13 to θ=0.26 monolayer are reported. The particles interact through an adsorbate–substrate potential previously derived and through a classical adsorbate–adsorbate Morse-type potential. Interesting results concerning the nature of the adsorbed phase have been obtained: (a) We have found that the potassium adlayer is incommensurate under 1 ML coverage (θ=0.25), but it becomes commensurate at 1 ML, forming a p(2×2) adlayer with respect to the Cu substrate. (b) A procedure to determine the distribution of potassium on different adsorption sites in terms of θ has been developed with the result that top sites are the preferred sites for adsorption, although at low and medium coverages other sites are also occupied. At 1 ML only the top sites are occupied, in good agreement with the available experimental data.