Modeling the H5+ potential-energy surface:: a first attempt

Ab initio molecular electronic structure calculations are performed for H-5(+) at the QCISD(T) level of theory, using a correlation-consistent quadruple-zeta basis set. Structures, vibrational frequencies and thermochemical properties are evaluated for ten stationary points of the H-5(+) hypersurface and are compared with previous calculations. The features of the H-3(+)... H-2 interaction at intermediate and large intermolecular distances are also investigated. Furthermore, an analytical functional form for the potential-energy surface of H-5(+) is derived using a first-order diatomics-in-molecule perturbation theory approach. Its topology is found to be qualitatively correct for the short-range interaction region.