The structure of fluid dichlorodifluoromethane. A comparison between molecular dynamics simulation and neutron diffraction results

Molecular dynamics simulations have been combined with neutron diffraction data in a study of the liquid structure of dichlorodifluoromethane (CFC-12). The radial distribution functions reveal a similar local structure to that encountered in carbon tetrachloride, where neighbouring molecules predominantly adopt what we term a ‘straddle’ conformation. Further ordering is found to exist in the case of CFC-12, however, due to the different polarizabilities of chlorine and fluorine. This results in a nonstatistical distribution of intermolecular nearest neighbours, where the probability of F-F close contacts is 60% of that of Cl-Cl close contacts, whereas the probability of F-Cl close contacts is 85% of that of Cl-Cl close contacts. The results also indicate that the average liquid structure is similar to the recently determined crystal structure.