Despite diminishing (and ultimately vanishing) monomer dipole moments along the planarization coordinate, electrostatic interactions remain significant. What is plotted in Fig. is actually polarized electrostatics (E elst +E ind ), but this sum is dominated by E elst at all geometries and when the monomers are planar (so µ = 0), E elst + E ind remains within 1 kcal/mol of its value in the equilibrium geometry. In fact, the total interaction energy (E int ) is slightly more stabilizing when the monomers are planar. Note that E int does not include the penalty to deform the monomers, and is simply the interaction energy for moving the rigid monomers to infinite separation. These calculations demonstrate that it is this deformation penalty, rather than any intermolecular driving force, that explains why (C 20 H 10 ) 2 adopts a geometry involving curved monomers. This cannot be explained based on the dipole moment induced by the curvature.