A DFT-based potential energy surface for the H7+ cluster

A global potential energy surface (PES) for the H?7+ complex is presented based on density functional theory (DFT) calculations. We used the B3(H) hybrid functional, a specifically parameterized B3LYP functional for hydrogen-only systems, and we first characterize the equilibrium H?7+ structure. In turn, by comparing with coupled clusterwith single, double and perturbative triples excitations (CCSD(T)) results, we show that the B3(H) predictions are in overall satisfactory and quantitative good agreement with these higher accurate ab initio data for all aspects of the potential, including the correct estimates asymptotic behavior at long H?5+ + H2 distances. Moreover, using the present surface we compute dissociation energies and dissociation enthalpies for the equilibrium H?7+ ? H?5+ + H2 reaction, and compare them with the data available from experimental measurements. In general, a very good accord is found, with the theoretical values from both DFT/B3(H) and CCSD(T) computations to predict somehow a less bound H?7+ cluster than the experimental estimates. Such realistic representations of the potential surfaces of polyatomic systems are of particular interest for studying spectroscopy, collision, and/or fragmentation dynamics, and this is the first attempt for a reasonable description of the H?7+ PES suitable for future direct dynamics simulations. (C) 2012 Wiley Periodicals, Inc.