CURVATURE VERSUS NUCLEAR-RELAXATION CONTRIBUTIONS TO THE STATIC VIBRATIONAL POLARIZABILITY OF POLYACETYLENE CHAINS

The nuclear relaxation and curvature contributions to the static vibra tional polarizability of all-trans polyacetylene chains have been calc ulated at the Hartree-Fock 6-31G level of approximation by using a fin ite field relaxation procedure. In the curvature contribution are incl uded the zero-point vibrational averaging and anharmonicity correction s to the double harmonic approximation which accounts for the nuclear relaxation term. From our calculations, the curvature contribution to the longitudinal component of the polarizability tensor per CH=CH unit equals 5.7 +/- 0.3 au, whereas the corresponding nuclear relaxation a nd electronic terms amount to 13.1 +/- 0.1 and 164+/-0.1 au, respectiv ely.