AB-INITIO STUDY OF THE INVERSION BARRIER IN NF3+

Ab initio Hartree-Fock, Moller-Plesset perturbation theory (MP2), and quadratic configuration interaction, using single and double substitut ions (QCISD), calculations were carried out for the NF3+ ion. Optimize d structures were examined at the various levels of theory. Calculatio n of the inversion barrier height shows the importance of optimizing t he geometry at the post-Hartree-Fock level and the inclusion of polari zation functions. The best calculated inversion barrier was 13.3 kcal/ mol, compared to an experimental value of 17.3 kcal/mol. The dissociat ion transition state was computed to determine the well depth of the N F3+ ion and its stability toward dissociation. The computed well depth was 28 and 48 kcal/mol at the SCF and MP2 levels, respectively. (C) 1 994 John Wiley & Sons, Inc.