Theoretical Characterization of the Minimum-Energy Structure of (SF6)2

MP2 and symmetry-adapted perturbation theory calculations are used in conjunction with the aug-cc-pVQZ basis set to characterize the SF6 dimer. Both theoretical methods predict the global minimum structure to be of C2 symmetry, lying 0.07-0.16 kJ/mol below a C2h saddle point structure, which, in turn, is predicted to lie energetically 0.4-0.5 kJ/mol below the lowest-energy D2d structure. This is in contrast with IR spectroscopic studies that infer an equilibrium D2d structure. It is proposed that the inclusion of vibrational zero-point motion gives an averaged structure of D2d symmetry.