The system energetics are strongly influenced by the distances between adsorbates and, thus, by the specific adsorbate arrangement on the 3 × 3 slab for a given coverage in 1/9 th -monolayer increments. We utilized two approaches to generate different configurations for CO on Pt(111): a simplistic configuration in which the same binding site is chosen, and a more accurate global minimum configuration. For the simplistic configuration, both atop site binding (atop-NN) and fcc hollow site binding (fcc-NN) configurations were considered. These configurations were accomplished with minimal computational effort. The first CO * was placed on a vacant site on the Pt surface. Next, a subsequent adsorbate was placed on a nearest-neighboring (NN) site to the first adsorbate. Once all the NN sites were occupied, the next NN sites were filled. The structures were optimized after each adsorbate placement. One exception of such arrangement was made to keep all adsorbates on atop sites for atop-NN 6/9 ML, where the center adsorbate is absent to prevent any migration to other sites. Because of the well-known discrepancy between the experimentally observed CO binding site (atop site) and the DFT-calculated lowest energy binding site (fcc hollow site) , both sites were chosen to attain two different simplistic configuration models.