Ab initio molecular orbital studies of the vibrational spectra of the van der Waals complexes of boron trifluoride with the noble gases

The molecular structures, interaction energies, charge transfer properties and vibrational spectra of the van der Waals complexes formed between boron trifluoride and the noble gases neon, argon, krypton and xenon have been computed using second and fourth order Møller-Plesset perturbation theory and the Los Alamos National Laboratory LANL2DZ basis set. The complexes are all symmetric tops, with the noble gas atom acting as a σ electron donor along the C3 axis of the BF3 molecule. The interaction energies are all vanishingly small, and the amount of charge transferred in each case is of the order of 0.01e. The directions of the wavenumber shifts of the symmetric bending (ν2) and antisymmetric stretching (ν3) modes of the BF3 fragment confirm those determined experimentally, and the shifts are shown to correlate well with the polarizability of the noble gas atom and the inverse sixth power of the intermonomer separation. The ν2 mode is substantially more sensitive to complexation than the ν3 vibration.