Curvature versus nuclear relaxation contributions to the static vibrational polarizability of polyacetylene chains

The nuclear relaxation and curvature contributions to the static vibrational polarizability of all-trans polyacetylene chains have been calculated at the Hartree-Fock 6-31G level of approximation by using a finite field relaxation procedure. In the curvature contribution are included the zero-point vibrational averaging and anharmonicity corrections 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 and electronic terms amount to 13.1 ± 0.1 and 164 ± 0.1 au, respectively.