Electronic potential energy surfaces for the reaction K+NaCl=KCl+Na

Abstract

The six lowest σ-bonded potential surfaces for the reaction K+NaCl=KCl+Na have been calculated on a semi-empirical model with a single valence electron in the field of the three closed shell ions. A simple method is proposed by which the energetic effects of valence-core orthogonalization, which are of crucial importance in the calculations, may be included in the potentials of the ions. Test calculations on the ions Na₂ ⁺ and K₂ ⁺ are in good agreement with experiment. The lowest potential surface is of the early downhill attractive type with no activation barrier. A 13·5 kcal/mole potential well is predicted at the configuration r _NaCl=2·7 Å, r _KCl=2·9 Å, NaĉlK=75°. At thermal energies reaction can occur for 50° < NaĉlK < 180°, and an adiabatic reaction mechanism is expected. An order of magnitude estimate of the reaction cross section is given by σ ∼ 30(1+10/E) Ų, where E (kcal/mole) is the initial energy of relative motion.