Effects of molecular electric potential and anisotropic atomic repulsion in the dichlorine dimer and crystalline chlorine

Molecular packing analysis of crystalline dichlorine (Cl-2) shows that the crystal structure is compatible with an isotropic intermolecular force field that includes polar flattening of the exchange repulsion energy and a five-center distributed monopole representation of the molecular electric potential. Polar flattening largely accounts for the short intermolecular contacts in the crystal, and the molecular electric potential is critical in determining the molecular orientation and space group. Neither an atom-centered model for repulsion nor a molecular quadrupole model for the electric potential is adequate to describe the force field of this molecule.