Water adlayers on noble metal surfaces: Insights from energy decomposition analysis

Water molecules adsorbed on noble metal surfaces are of fundamental interest in surface science, in heterogeneous catalysis, and as a model for the metal/water interface. Herein, we analyze 28 water structures adsorbed on five noble metal surfaces (Cu, Ag, Au, Pd, and Pt) via density functional theory and energy decomposition analysis based on the block localized wave function technique. Structures, ranging from monomers to ice adlayers, reveal that the charge transfer from water to the surface is nearly independent from the charge transfer between the water molecules, while the polarization energies are cooperative. Dense water-water networks with small surface dipoles, such as the 39×39 unit cell [experimentally observed on Pt(111)], are favored compared to the highly ordered and popular H^up and H^down phases. The second main result of our study is that the many-body interactions, which stabilize the water assemblies on the metal surfaces, are dominated by the polarization energies, with the charge transfer scaling with the polarization energies. Hence, if an empirical model could be found that reproduces the polarization energies, the charge transfer could be predicted as well, opening exciting perspectives for force field development.