Water on the MgO(001) Surface: Surface Reconstruction and Ion Solvation

The interaction of water with the MgO(001) surface under ambient conditions is investigated by density functional theory combined with statistical thermodynamics. For water loadings of more than one monolayer, we show that the standard structure model, a fully hydroxylated surface, needs to be revised. Reconstructed surfaces, involving hydrated/hydroxylated Mg(2+) ions above the surface, are more stable. These findings provide a consistent picture for surface hydroxylation between low and high water coverage that is in agreement with available XPS data.