Structure and dissociation energy of weakly bound H 2 n +1 + ( n = 5−8) complexes

The geometrical parameters, vibrational frequencies, and dissociation energies for H   2n+1 +(n = 5–8) clusters have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The highest level of theory employed in this study is TZ2P CCSD(T). The C 1 structure of H   15 +is predicted to be a global minimum, while the C s structure of H   15 +is calculated to be a transition state. Harmonic vibrational frequencies are also determined at the DZP and TZ2P CCSD levels of theory. The dissociation energies, D e , for H   2n+1 +(n = 5–8) have been predicted using energy differences at each optimized geometry, and zero‐point vibrational energies (ZPVEs) are considered to compare with experimental values. The dissociation energies ( D o ) have been predicted to be 1.69, 1.65, 1.65, and 1.46 kcal · mol for H   11 + , H   13 + , H   15 +( C 1 symmetry) and H   17 + , respectively, at the TZ2P CCSD(T) level of theory. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007