Geometries and Binding Energies of Hn+

Abstract

Ab initio calculations were made for H_n⁺(n=4, 5, 6), with simple Gaussian orbital wavefunctions. Their geometries were determined by minimizing the total energy with respect to relative proton positions. The stable ions, their geometries, electronic symmetries, and estimated binding energies are: H₄⁺, planar C_2v, ²A₁, 0.54 eV; and H₅⁺, D_2d, ¹A₁, 0.81 eV: H₆⁺ is unstable. The electron densities and vibration frequencies of H₄⁺ and H₅⁺ were also calculated. A hydrogen‐bond model is proposed for the binding of H₄⁺ and H₅⁺ (with extensions to H₆⁺ and H₇⁺). The importance of this model for kinetics of certain ion reactions is discussed.