Localization properties of .pi. electrons and the validity of independent-particle models for hydrocarbon compounds

The electronic localization properties in alternant and nonalternant hydrocarbon π compounds are quantified in terms of the mean-square deviation of the π electron density around the corresponding mean value . To derive the correlated ground state, the method of the local approach (LA) is employed. The computational method for the π subspace is a simple Huckel-type operator for the one-determinantal wave function and a model Hamiltonian defined by Hartree-Fock hopping terms to evaluate the correlated ground state