Homogeneous and mixed UF6 clusters with Ar: Calculations of structures and vibrational spectra

Abstract

A recently developed site–site intermolecular potential for UF6, featuring exchange, dispersion, and electrostatic terms, is used to calculate minimum energy structures of homogeneous UF6 clusters up to the decamer. The structures of mixed (UF6)2–Arn clusters are also calculated by adding appropriate interaction terms. The IR spectra corresponding to the determined cluster structures in the region of the ν3 vibrational mode of the monomer (at 627.724 cm−1) are calculated using a second-order line shift formalism, treating the anharmonic intramolecular force field and the intermolecular potential as a perturbation. The leading interaction mechanism responsible for the line shifts of the ν3 mode is found to be the electrostatic one (implicitly the resonant dipole–dipole coupling). The theoretical spectra are shown to satisfactorily describe the peaks around 623, 632, and 640 cm−1 found in the recently measured Fourier transform IR spectra in a continuous supersonic Laval nozzle flow and attributed to the clusters formed by UF6.