Comparison of SCF-Xα-SW and CNDO/BW calculations on S4N4H4and F4S4N4

Theoretical calculations on the molecules S4N4H4 and F4S4N4 were made using the SCF-Xα-SW and CNDO/BW methods. In the SCF-Xα-SW method the parameterization with overlapping spheres gave better orbital energies than the parameterization with touching spheres. The eigenvalues and point charges calculated with the SCF-Xα-SW overlap parameterization were in excellent agreement with those calculated with the CNDO/BW method. In the SCF-Xα-SW method, d-orbitals were found to have an insignificant effect on the eigenvalues and point charges. The (CNDO-BW) Localized Molecular Orbitals, LMO's, are highly localized, and give bent SN bonds with a bond order of 1. The two different bond SN distances in F4S4N4 are due to hybridization changes at the suphur and nitrogen atoms.