A First Principles Development of a General Anisotropic Potential for Polycyclic Aromatic Hydrocarbons

Standard empirical atom-atom potentials are shown to be unable to describe the binding of polycyclic aromatic hydrocarbon (PAH) molecules in the variety of configurations seen in clusters. The main reason for this inadequacy is the lack of anisotropy in these potentials. We have constructed an anisotropic atom-atom intermolecular potential for the benzene molecule from first principles using a symmetry-adapted perturbation theory based on density functional theory (SAPT(DFT)), interaction energy calculations and the Williams-Stone-Misquitta method for obtaining molecular properties in distributed form. Using this potential as a starting point, we have constructed a transferable anisotropic potential to model intermolecular interactions between PAHs. This new potential has been shown to accurately model interaction energies for a variety of dimer configurations for four different PAH molecules, including certain configurations which are poorly modeled with current isotropic potentials. It is intended that this potential will form the basis for further work on the aggregation of PAHs.