Modeling the subsurface adsorption of atomic oxygen in silver from high vacuum to high pressure

Coadsorption of atoms or molecules on a solid can modulate adsorption energies, adsorbate geometries, surface reconstructions, and surface reactions. Interactions between atomic adsorbates at higher coverages can even promote percolation of some atoms beneath the surface into the subsurface or deeper into the bulk of the solid. The evolution of surface phenomena and the emergence of subsurface adsorption with increasing coadsorption effects are less understood at the atomic level due to the experimental and theoretical challenges of studying larger surface coverages. Yet, important practical applications, such as metal oxidation, corrosion, and industrial heterogeneous catalysis occur at high adsorbate concentrations and require a fundamental understanding of adsorption and reactivity over a wide range of coverages. Here, we develop an all-site, ab initio, lattice-gas model that describes surface and subsurface adsorption in a crystalline solid and apply it to study the adsorption of atomic oxygen on the Ag(111) surface at varying oxygen concentrations and O₂ pressures ranging from high vacuum to high pressure. The coadsorbate interactions in the model are treated in a pairwise manner and all parameters of the model are calculated using density functional theory. This study demonstrates that three-dimensional lattice-gas models can be powerful theoretical tools to predict the conditions for subsurface adsorption and elucidate the underlying inter-adsorbate interactions.