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We present a kinetic Monte Carlo lattice gas model including top and bridge sites on a square lattice, with pairwise lateral interactions between the adsorbates. In addition to the pairwise lateral interactions we include an additional interaction: an adsorbate is forbidden to adsorb on a bridge site formed by two surface atoms when both surface atoms are already forming a bond with an adsorbate. This model is used to reproduce the low and high coverage adsorption behaviour of CO on Pt(100) and Rh(100). The parameter set used to simulate CO on Pt(100) produces the c(2 x 2)-2t ordered structure at 0.50 ML coverage, a one-dimensionally ordered structure similar to the experimentally observed (3 square root(2) x square root(2)) - 2t + 2b structure at 0.67 ML coverage, the c(4 x 2)-4t + 2b ordered structure at 0.75 ML coverage, and the recently reported c(6 x 2)-6t + 4b ordered structure at 0.83 ML coverage. The (5 square root(2) x square root(2)) ordered structure at 0.60 ML coverage is not reproduced by our model. The parameter set used to simulate CO on Rh(100) produces the c(2 x 2)-2t ordered structure at 0.50 ML coverage, a one-dimensionally ordered structure similar to the experimentally observed (4 square root(2) x square root(2)) - 2t + 4b structure at 0.75 ML coverage, and the c(6 x 2)-6t + 4b ordered structure at 0.83 ML coverage. Additionally, the simulated change of top and bridge site occupation as a function of coverage matches the trend in experimental vibrational peak intensities.

Lateral adsorbate-adsorbate interactions result in variation of the desorption rate constants with coverage. This effect can be studied in great detail from the shape of a multi-isotherm. To produce the multi-isotherm, the temperature is increased in a (semi)stepwise fashion to some temperature, followed by maintaining this temperature for a prolonged time. Then, the temperature is stepped to a higher value and held constant at this new temperature. This cycle is continued until all of the adsorbates have desorbed. Using a detailed kinetic Monte Carlo model and an optimization algorithm based on Evolutionary Strategy, we are able to reproduce the shape of the experimentally measured multi-isotherm of nitrogen on Rh(111) and obtain the lateral interactions between the nitrogen atoms.

The adsorption of a bridge-bonded molecule onto fcc͑100͒ and fcc͑111͒ surfaces is studied using kinetic Monte Carlo simulations. The results are related to examples from both the electrochemical and the ultrahigh vacuum field. The lateral interaction model for the fcc͑100͒ surface with the least excluded neighbor sites does not cause ordering in the adlayer at saturation coverage. This is due to the availability of two equivalent bridge sites per surface atom. The model with the most excluded sites on the other hand causes the formation of a c͑4 ϫ 2͒ ordered structure with a coverage of 0.25 ML. Surprisingly, for the model with intermediate-ranged lateral interactions a one-dimensionally ordered structure is found. In this one-dimensionally ordered structure, bridge-bonded anions are aligned along the ͱ 2 direction. The spacing between these rows varies, since each new row can form at either one of the two kinds of bridge site per surface atom. The local distribution between these one-dimensional rows can be described by, respectively, a c͑2 ͱ 2 ϫ ͱ 2͒ or a ͑ ͱ 2 ϫ ͱ 2͒ unit cell ͓the latter one is also referred to as c͑2 ϫ 2͔͒. On the fcc͑111͒ surface, once again no ordered structure is found for the model with the smallest number of excluded sites. For the models with more excluded sites a c͑4 ϫ 2͒ ordered structure ͓also known as c͑2 ϫ ͱ 3͔͒ and a ͑ ͱ 3 ϫ ͱ 7͒ ordered structure are formed, the coverages being 0.50 and 0.20 ML, respectively. The simulated voltammograms generally show a broad peak due to adsorption in a disordered phase, and, if a two-dimensionally ordered structure is formed, a second sharp peak due to a disorder-order transition in the adlayer. The formation of the one-dimensionally ordered structure does not cause an additional current peak in the voltammogram.