The electrochemical interface between a corroding material’s surface and the ambient aqueous media is central to the material’s behavior. Using quantum chemical methods (DFT), we have investigated the atomic-scale structure and composition of the electrochemical interface of copper (Cu) and chalococite (Cu₂S) as formed under anoxic corrosion of copper in sulfide-containing media. The influence of common groundwater ions including HS^-, Cl^-, SO₄^2- and HCO₃^- that will be present in the proposed Swedish, Finnish and Canadian deep geological repositories (DGRs) for disposal of spent nuclear fuel are investigated. To make the modeling as realistic as possible, we have applied the latest methods for including the effects of pH and corrosion potential in our simulations. Where available, our results are discussed in comparison to experimental data, in particular cyclic voltammograms. It is found that under expected DGR conditions, most of the low index surfaces of Cu and Cu₂S will be covered by adsorbed sulfides. Notable exceptions include Cu₂S surfaces covered by SO₄^2-. The implications of our results are discussed in connection to copper corrosion rate in sulfide-containing media and Cu₂S corrosion film morphology.

DFT modeling, copper corrosion, groundwater ions, pH and potential effects7th International Workshop on Long-term Prediction of Corrosion Damage in Nuclear Waste Systems (LTC 2019)