Modeling the H-5(+) 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 quadrup le-zeta basis set. Structures, vibrational frequencies and thermochemical p roperties are evaluated for ten stationary points of the H-5(+) hypersurfac e and are compared with previous calculations. The features of the H-3(+).. . H-2 interaction at intermediate and large intermolecular distances are al so investigated. Furthermore, an analytical functional form for the potenti al-energy surface of H-5(+) is derived using a first-order diatomics-in-mol ecule perturbation theory approach. Its topology is found to be qualitative ly correct for the short-range interaction region.