From uncoupled to coupled Hartree–Fock polarizabilities of infinite polymeric chains. Pariser–Parr–Pople applications to the polyacetylene chains

A general method is formulated to compute the asymptotic longitudinal polarizabilities of infinite systems. This procedure is an extension to infinite systems of the molecular random-phase-approximation method which provides coupled Hartree–Fock values and thus takes into account the field-induced electron reorganizational effects. It is shown that the Genkin–Mednis uncoupled method corresponds to the drastic approximation of the coupled one where there is no electron reorganization. By looking at the asymptotic polarizabilities as the convergence values of the oligomeric results, the method is tested for polyacetylene chains in the Pariser–Parr–Pople approximation.