ON OBTAINING LOCALIZED BONDING SCHEMES FROM DELOCALIZED MOLECULAR-ORBITAL WAVE-FUNCTIONS

A straightforward procedure is proposed for expanding a molecular orbi tal determinantal wave function into a set of determinantal wave funct ions composed of atomic orbitals localized at the atoms of a molecule. By employing this method, atomic orbital determinants and their weigh ts can be derived for a molecule from the computed molecular-orbital w ave function. The procedure permits the interpretation of a molecular orbital determinantal wave function in terms of bonding schemes relate d to the classic resonance structures used by organic chemists. By usi ng the unrestricted molecular orbital determinant, bonding schemes and their weights are obtained for butadiene, the butadiene radical catio n and the acrylonitrile radical anion. Their dominant bonding schemes are in accord with the relevant resonance structures for these molecul es. For the butadiene radical cation and the acrylonitrile anion they are shown to be compatible with the accepted mechanisms of the electro chemical coupling reactions of butadiene and acrylonitrile.