Ab initio polarizabilities calculations of singly charged polyacetylene oligomers

We present results for the static longitudinal linear polarizability and se cond-order hyperpolarizability of small polyacetylene chains bearing positi vely and negatively charged solitons, obtained through the second-order Mol ler-Plesset perturbation theory (MP2) method. Hartree-Fock (HF) calculation s for these properties was performed only for negatively charged chains. Th e standard 6-31G basis set was used in all calculations. Our ab initio calc ulations showed that, regarding singly charged structures, only the second hyperpolarizability is affected by the ionization state. For both, positive and negative structures, it is shown that the electron correlation effect enhances the linear polarizability, and even more markedly the second hyper polarizabilities. (C) 2001 Elsevier Science B.V. All rights reserved.