The DFT values obtained in this work at low oxygen ratios (∆ ḠO ≈ 1.2 eV) are -0.3 eV lower than expected values for Pt(111) using the same functional (PBE). In our case this is explained by the large presence of oxygen atoms on two-fold bridge sites (Figure ) placed by MACE-MP-0. Such sites have been shown to be more stable than typical 3-fold, fcc or hcp sites by C. Jennings et al. on a smaller, perfect nanoparticle. Interestingly, MACE-MP-0 did place oxygen atoms on these sites during the Monte Carlo simulations, but cannot predict the correct extent of stabilization, resulting in a large discrepancy with DFT. This underscores the challenges associated with accurately computing lateral coefficients for non-ideal catalysts, such as our Pt nanoparticle. These difficulties stem from the complex interplay between the varying stabilities of different surface sites and the real interactions among adsorbates. Notably, at low oxygen coverage, a significantly wider range of configurations become accessible, leading to a diverse range of energetically distinct configurations.