A more nuanced picture emerges for the dimer of 1,3,5triazine, for which one-dimensional potentials are plotted in Fig. at the same three values of R that were considered for (thiophene) 2 , and in a configuration where the monomer dipole moments are parallel to one another. The total interaction potential exhibits a slip-stacked double-minimum at all three values of R but E vdW exhibits only a single minimum (corresponding to perfect cofacial stacking) for R 3.9 Å. The total interaction potential continues to exhibit a double minimum even at these larger values of R, and in this case that doubleminimum structure emerges from E elst rather than E vdW . That said, the double minimum in E int is rather shallow and E vdW remains a reasonable match for the magnitude of this attractive potential. If one of the monomers is rotated by 180 • , so that the dipole moment vectors are antiparallel, then E elst becomes more (and strictly) attractive at R = 3.4 Å, as shown in Fig. . In this case, E int exhibits only a single minimum, corresponding to cofacial π-stacking that is driven by E elst . The vdW potential is essentially unaf- fected by this 180 • rotation and maintains its double-well structure in the antiparallel orientation. It is responsible for flattening out the potential surface for lateral displacements, enabling offset-stacking to emerge on the rather flat E int surface.