Interatomic potential for the Cu-Ta system and its application to surface wetting and dewetting

An angle- dependent interatomic potential has been developed for the Cu- Ta system by crossing two existing potentials for pure Cu and Ta. The cross- interaction functions have been fitted to first- principles data generated in this work. The potential has been extensively tested against first- principles energies not included in the fitting database and applied to molecular dynamics simulations of wetting and dewetting of Cu on Ta. We find that a Cu film placed on a Ta ( 110 ) surface dewets from it, forming a Cu droplet on top of a stable Cu monolayer. We also observe that a drop of liquid Cu placed on a clean Ta ( 110 ) surface spreads over it as a stable monolayer, while the extra Cu atoms remain in the drop. The stability of a Cu monolayer and instability of thicker Cu films are consistent with recent experiments and first- principles calculations. This agreement demonstrates the utility of the potential for atomistic simulations of Cu- Ta interfaces.