ONIOM(QM:AMOEBA09) Study on Binding Energies and Binding Preference of OH, HCO, and CH3 Radicals on Hexagonal Water Ice (Ih)

Abstract

We have combined the AMOEBA09 polarizable force field with the ONIOM(QM:MM) method to rationalize binding energies and binding preferences of the OH, HCO, and CH3 radicals on crystalline water ice (Ih). ONIOM(M062X:AMOEBA09) and ONIOM(wB97XD:AMOEBA) calculations suggest that the dangling hydrogen (d-H) or dangling oxygen (d-O) on the binding sites play an important role on the binding energies. Depending on the dangling nature at the binding site, a range of binding energies is found for the OH radical (0.67–0.20 eV), HCO radical (0.42–0.12 eV), and CH3 radical (0.26–0.11 eV). The binding energies of these radicals are larger in the presence of both d-H and d-O at the binding site. On the other hand, binding energies are weaker in the presence of only d-H or d-O at the binding site. The ONIOM(QM:AMOEBA09) methodology is found to be a useful approach to calculate binding energies of atoms, radicals, and molecules on Ih.