Approximate Self-Consistent Molecular-Orbital Theory. V. Intermediate Neglect of Differential Overlap

Abstract

A new approximate self-consistent-field method for the determination of molecular orbitals for all valence electrons of a molecule is proposed. This method features neglect of differential overlap in all electron-interaction integrals except those involving one center only. The parameters involved in the calculation are generally obtained semi-empirically. The new method is known as the Intermediate Neglect of Differential Overlap (INDO) method, and may be regarded as an improvement over the CNDO method proposed in Part I, in that atomic term-level splittings and unpaired spin distributions are better accommodated. Calculations on geometries of AB2 and AB3 molecules are reported to substantiate the proposed method, and calculated unpaired spin distributions for methyl and ethyl radicals are discussed.