Differences in the sublimation energy of benzene and hexahalogenbenzenes are caused by dispersion energy.

The crystals of benzene and hexahalogenbenzenes have been studied by means of the density functional theory augmented by an empirical dispersion correction term as well as by the symmetry-adapted perturbation theory. In order to elucidate the nature of noncovalent binding, pairwise interactions have been investigated. It has been demonstrated that the structures of dimers with the highest stabilization energy differ notably along the crystals. It has been shown that the differences in the experimental sublimation energies might be attributed to the dispersion interaction. To our surprise, the dihalogen bonding observed in the hexachloro- and hexabromobenzenes plays a rather minor role in structure stabilization because it is energetically comparable with the other binding motifs. However, the dihalogen bond is by far the most frequent binding motif in hexachloro- and hexabromobenzenes.