Applications of a simple molecular wavefunction. Part 5.—Floating Spherical Gaussian Orbital open-shell calculations: introduction

Abstract

A procedure is described for applying the Floating Spherical Gaussian Orbital (FSGO) model to molecular systems in doublet ground states. Results are presented for several three-electron systems. For the transition state of the hydrogen atom/hydrogen molecule exchange reaction, a linear arrangement of the nuclei is preferred over a triangular one in agreement with other calculations. However, the activation energy is too large. The FSGO model, using two configurations, is able to produce a van der Waals type interaction both between H and H₂ and between H and He. Although the energy of interaction is not as large as would be expected from their polarizabilities, the HeH system is predicted to be several times more stable than a possible H … H₂ complex. A good internuclear distance and dissociation energy are calculated for He⁺ ₂. A low dissociation energy is computed for LiH⁺. Various forms of H⁺ ₄ have been studied. It is shown that it is possible for it to exist as a complex between H and H⁺ ₃; this being preferred to one between H₂ and H⁺ ₂. Each three-electron FSGO wavefunction is fully optimised in 10–15 seconds CPU time (Cambridge Titan Computer; estimated time on the IBM 270/165 is less than ½ second).