Hybrid DIM-based QM/MM approach applied to vibrational spectra and trapping site structures of HArF in solid argon

Vibrational spectra and trapping sites of HArF in solid argon are studied by using the original hybrid approach, combining quantum mechanical (QM) description of HArF at the MP2/6-311++G(2d,2p) level and non-empirical diatomics-in-molecules (DIM) method for guest-host interactions. Three types of structures for trapping sites within the C4v (DS-I), C2v (DS-II) and C3v (DS-III) local symmetries are found. The calculated differences in harmonic frequencies of the H-Ar stretching and H-Ar-F bending vibrations between these sites are in quantitative agreement with the experimental data. The results indicate that the thermally stable solid-state configuration of HArF can be best described by the DS-III structure, while the unstable configuration refers to DS-I.