Theoretical study of the relative stabilities of H + ( X ) 2 and H + ( X ) 3 conformers and their clustering energies: X  CO and N 2

Third‐order Møller–Plesset perturbation theory ( MP 3) with a 6‐31G** basis set was applied to study the relative stabilities of H + ( X ) 2 conformations ( X CO and N 2 ) and their clustering energies. The effect of both basis set extensions and electron correlation is not negligible on the relative stabilities of the H + (CO) 2 clusters. The most stable conformation of H + (CO) 2 is found to be a C ∞ v structure in which a carbon atom of CO bonds to the proton of H + (CO), whereas that of H + (N 2 ) 2 is a symmetry D ∞ h structure. The second lowest energy conformations of H + (CO) 2 and H + (N 2 ) 2 lie within 2 kcal/mol above the energies of the most stable structures. Clustering energies computed using MP 3 method with the 6‐31G** basis set are in good agreement with the experimental findings of Hiraoka, Saluja, and Kebarle. The low‐lying singlet conformations of H + ( X ) 3 ( X CO and N 2 ) have been studied by the use of the Hartree–Fock MO method with the 6‐31G** basis set and second‐order Møller–Plesset perturbation theory with a 4‐31G basis set. The most stable structure is a T‐shaped structure in which a carbon atom of CO (or a nitrogen atom of N 2 ) attacks the proton of the most stable conformation of H + ( X ) 2 clusters.