Computational Study of the Interactions between Benzene and Crystalline Ice Ih : Ground and Excited States.

Ground-state geometries of benzene on crystalline ice cluster model surfaces (Ih ) are investigated. It is found that the binding energies of benzene-bound ice complexes are sensitive to the dangling features of the binding sites. We used time-dependent DFT to study the UV spectroscopy of benzene, ice clusters, and benzene-ice complexes, by employing the M06-2X functional. It is observed that the size of the ice cluster and the dangling features have minor effects on the UV spectral characteristics. Benzene-mediated electronic excitations of water towards longer wavelengths (above 170 nm) are noted in benzene-bound ice clusters, where the cross-section of photon absorption by water is negligible, in good agreement with recent experimental results (Thrower et al., J. Vac. Sci. Technol. A, 2008, 26, 919-924). The intensities of peaks associated with water excitations in benzene-ice complexes are found to be higher than in isolated ice clusters. The π→π* electronic transition of benzene in benzene-ice complexes undergoes a small redshift compared with the isolated benzene molecule, and this holds for all benzene-bound ice complexes.