Enhanced solubility on surfaces: Molecular-dynamics simulations of an Ag overlayer on Cu(100)

Using molecular-dynamics simulations, we calculate the energetics; of Ag de posited on Cu(100) surface and show that the driving force for substitution al surface alloying diminishes with increasing Ag coverage at 300 K. We fur ther demonstrate that even at the Ag saturation coverage of close to one mo nolayer, the apparent positive enthalpy of mixing in surface layers is redu ced relative to its value in the bulk and decreases with increasing tempera ture. As a result, intermixing between the reconstructed Ag overlayer and t he underlying Cu surface layer can be observed at moderately elevated tempe ratures, forming a surface alloy well beyond equilibrium solid solubility l imits.