Hartree-Fock static longitudinal polarizabilities of fluorinated polyacetylene chains

This work presents ab initio results for the static longitudinal linear polarizability, alpha, and second hyperpolarizability, gamma, of planar and twisted fluorinated polyacetylene chains. These electric properties were calculated by the finite field (FF) method, in the framework of the Hartree-Fock approximation. Our calculations, using different basis sets (6-31G and its standard extensions) indicate that inclusion of polarization functions, through the 6-31G(d) basis set, is important in the determination of the geometric parameters, specially dihedral angles. Nevertheless for both, planar and twisted F-substituted chains, our results show that the 6-31G basis set is sufficient to provide consistent estimates for alpha and gamma. It is observed that the twisted conformation of F-substituted compounds leads to a marked reduction on the polarizabilities, specially on the second hyperpolarizability. Using converged geometries, the polarizabilities for the polymeric polydifluoroacetylene chains were obtained by extrapolation and compared with those of polymeric polyacetylene chains. (C) 2004 Elsevier B.V. All rights reserved.