Calculations of structures and vibrational spectra of homogeneous and mixed SF6 clusters with Ar

A recently reported intermolecular potential for SF6, featuring exchange, dispersion, and electrostatic terms, is used to determine minimum energy structures of homogeneous SF6 clusters up to the decamer. By adding appropriate interaction terms, also structures of mixed (SF6)2-Arn clusters are calculated. A second order line shift formalism, treating the anharmonic intramolecular force field and the intermolecular potential as a perturbation, is employed to calculate the corresponding IR-spectra in the region of the ν3 vibrational mode of the monomer (at 947.968 cm ). The leading interaction mechanism responsible for the line shifts is confirmed to be the resonant dipole-dipole coupling. The theoretical spectra fairly describe both size-selected spectra for clusters up to the tetramer and recently measured FT-IR spectra in a continuous supersonic Laval nozzle flow. PACS. 36.40.Mr Spectroscopy and geometrical structure of clusters