In PBE and PBEsol, we see the addition of the Grimme terms increases the binding strength substantially. Changing from GD2 to GD3 in the case of PBE and PBEsol decreases the binding strength, whereas it increases the binding strength for revPBE and RPBE. The more striking difference is in the substantial change of the S-column motif upon addition of the Grimme terms. It is very far from being as stable as the S-diagonal motif for PBE and PBEsol, but becomes much more favorable with the introduction of the dispersion corrections. Examination of the structures sheds some light on why this is the case, as shown in Figure . For PBE, the addition of the Grimme terms induces an attraction that allows for the amines to attach to two nodes, which is not the case in standard PBE. There is also clear formation of hydrogen bonds with the secondary amine and the oxygen backbone. For PBEsol, it is doubly-attached even in the absence of dispersion corrections. However, the geometry is such that formation of a stabilizing hydrogen bond is only allowed when including GD2 or GD3.