DISPERSION INTERACTION OF CONJUGATED MOLECULES - ONE-ELECTRON AND MANY-ELECTRON MODELS

A scheme for calculating van der Waals constants C-6, C-8, and C-10 in terms of the full configuration interaction for pi-shells is suggeste d. The required imaginary frequency dynamic polarizabilities are also investigated with one-electron schemes. The variational perturbation t heory of the Hartree-Fock method considerably exaggerates the constant C-21; the conjugated variant of perturbation theory is preferable. Th e additive scheme for estimating the sigma-contribution allows one to calculate the energy of dispersion attraction in real conjugated syste ms, as demonstrated by semiempirical estimates of evaporation heat in butadiene, benzene, naphthalene, and phenylacetylene.