To examine this in a system where electrostatics plays an even more important role, energy profile contours for nitrobenzene dimer that are plotted in Fig. . By itself, the vdW potential affords a minimum-energy separation of R min ≈ 3.8 Å, whereas the correct value (considering all energy components) is about 3.4 Å. This difference is directly attributable to electrostatic interactions that are attractive at these distances, contrary to the quadrupolar electrostatics picture. In the case of (C 6 H 5 NO 2 ) 2 , short-range electrostatics is attractive regardless of whether the monomer dipole moments are aligned parallel or antiparallel; see Fig. ) for the parallel configuration and in Fig. (f) for the antiparallel arrangement.