Ab initio study on the effect of attaching a hydrogen molecule to the (H<inf>5</inf>O<inf>2</inf>)⁺ ion cluster

Ab initio energy calculations using the Møller-Plesset perturbation theory up to fourth order with the 6-31G(D,P) basis set have been performed for the H5O2+ ion cluster with and without a hydrogen molecule attached to it. In agreement with experimental results, a C2 structure which gives rise to only two high O-H stretching frequencies is predicted to be the only minimum of the isolated ion, whereas when H2 is present, again only one minimum is found which can be roughly assigned to be of the Cs type. This structure is predicted to have four active O-H stretching frequencies, again in agreement with the experimental spectrum. © 1992 American Institute of Physics.