The structure and interaction energies of the weak complexes of CHClF2 and CHF3 with HCCH: a test of density functional theory methods

The structure and interaction energies of the weak non-covalent complexes of CHClF2 and CHF3 with HCCH have been predicted using a number of density functional based approaches, and compared with both high resolution spectroscopic data recently reported by Sexton et al. [Phys. Chem. Chem. Phys., 2010, 12, 14263-14270], and with high level benchmark calculations reported herein. We find that this is another case where the M05 and M06 families of functionals, as well as the DFT-D approach, are competitive with the more costly wavefunction based methods. We highlight the problem of deriving unique intermolecular structural parameters from the experimental microwave data.