Properties of interfaces between copper and copper sulphide/oxide films

[Display omitted] •Facet-specific interface interactions provide enhanced insight of corrosion behaviour.•Different Cu facets have different tendencies to form Cu2S and Cu2O films.•A geometrical tool for assessing anisotropic interface matching is evaluated.•Bulk properties cannot directly predict properties of 1−2 nm Cu2O or Cu2S films.•Geometrical and thermodynamic arguments are complementary to predict film character. We compare different means of predicting and rationalizing properties of corrosion films aiming at gaining deeper understanding of the behaviour of copper in aqueous and sulphide-containing environments. Purely geometrical tools ranging from mean bulk information to anisotropic and facet-specific approaches are discussed, and their performances compared against DFT-based stability and property evaluations of a range of interfaces arising from combining low-index crystallographic planes of the compounds Cu, Cu2O, and Cu2S. We demonstrate the necessity to consider facet-specific interactions to understand nanolevel differences between Cu2S and Cu2O film behaviour, and that thin films cannot be directly described by bulk properties.