An increasing trend in the adsorption energy as a function of coverage is shown in Figure for Pt(111), indicative of repulsive coverage effects. Based on the shape of the curves, two different regions can be observed: a lesser repulsion at lower coverages, and a greater repulsion at higher coverages. The coverage effect for the low-coverage region is dominated by the adsorbate-surface interaction and the surface relaxation effect, whereas the coverage effect in the high-coverage region is predominantly determined by adsorbate-adsorbate interactions. More specifically, there is an onset of the lateral repulsion among CO * across ∼ 0.5 ML, as indicated in Figure . Therefore, the addition of lateral repulsion energy on top of the adsorbate-surface interaction and surface relaxation effect is responsible for the increased coverage dependence for θ > 0.5 ML.