  In this work, we investigate dispersion interactions in a selection of
atomic, molecular, and molecule-surface systems, comparing high-level
correlated methods with empirically-corrected density functional theory (DFT).
We assess the efficacy of functionals commonly used for surface-based
calculations, with and without the D3 correction of Grimme. We find that the
inclusion of the correction is essential to get meaningful results, but there
is otherwise little to distinguish between the functionals. We also present
coupled-cluster quality interaction curves for \ce{H2} and \ce{NO2} interacting
with large carbon flakes, acting as models for graphene surfaces, using novel
absolutely localised molecular orbital based methods. These calculations
demonstrate that the problems with empirically-corrected DFT when investigating
dispersion appear to compound as the system size increases, with important
implications for future computational studies of molecule-surface interactions.
