Ab initio structure calculations of hydrogen ionic clusters

Ab initio molecular electronic-structure theory has been used in an attempt to characterize the low-lying stationary points on the potential energy hypersurface of positive ionic hydrogen clusters. Using triple-zeta-plus-polarization basis sets, self-consistent-field Hartree-Fock calculations, configuration-interaction calculations with single + double substitutions and fourth-order Moller-Plesset calculations have been carried out for H(n)+, n = 3 to 9 (odd). Dissociation energies as a function of cluster size follow the most recent experimental data. To our knowledge, the present study represents the best theoretical prediction for H7+ and H9+.