Correlation effects and electron delocalization in nonalternant hydrocarbon .pi. compounds

Many-particle contributions to the π-electronic structure of nonalternant hydrocarbons are investigated by a local correlation approach. Numerical results are derived by adopting a simple tight-binding model as well as a model operator in the zero-differential overlap (ZDO) approximation definded in terms of the Hartree-Fock hopping element. The different integrals are calculated ab initio in a Slater-type basis. The atomic π-electron density localization is quantified by the charge fluctuations corr in the correlated ground state |ψ 0 >