Ionization potentials and bond lengths for CO, N2, and F2using the SCF-Xα-SW method: A study of the effect of overlapping spheres

Abstract

Using a simple, arbitrary, but fixed procedure for the choice of sphere sizes in the overlapping sphere version of the SCF-Xα-SW method, results for the ionization potentials of CO, N₂, F₂, and H₂O are in considerably better agreement with experiment than those of the muffin-tin version. The agreement is as good as those of the SCF-Hartree-Fock, Discrete Variational-Xα, and LCAO-Xα methods. For the first time the overlapping sphere modification has been used to calculate binding curves and results in equilibrium bond lengths for CO, N₂, and F₂ all within 0·3 a ₀ (0·16 Å) of the experimental values, a dramatic improvement over the muffin-tin results. The variation of the calculated ionization potentials under a moderate change in the amount of sphere overlap is found to be rather small, being of the order of the differences between the DV-Xα and LCAO-Xα methods, both of which completely avoid the muffin-tin approximation.