Knowledge Bank

An improved intermolecular potential surface for the benzene dimer has been constructed from interaction energies computed by symmetry-adapted perturbation theory with the inclusion of third-order contributions. The potential was used in calculations of vibration-rotation-tunneling levels of the dimer by a method appropriate for large amplitude intermolecular motions and tunneling between multiple equivalent minima in the potential. The resulting levels were analyzed using the permutation-inversion full cluster tunneling group $G576$ and a chain of subgroups that starts from the molecular symmetry group $Cs$(M) of the rigid dimer at its equilibrium $Cs$ geometry and leads to $G576$ if all possible intermolecular tunneling mechanisms are feasible.