We here want to understand how variations in functional choice and van der Waals treatment affect the qualitative and quantitative prediction of amine binding energy, and how that affects the predicted loading and motif. We explore the Perdew-Burke-Ernzerhof (PBE) functional and its formulation for solids (PBEsol) with and without the Grimme-D2 and Grimme-D3 pairwise corrections (PBE+D2/3 and PBEsol+D2/3), two revised PBE functionals with the Grimme-D2 and Grimme-D3 pairwise corrections (RPBE+D2/3 and revPBE+D2/3), and the non-local van der Waals correlation (vdW-DF2) functional .