CONFORMATIONAL PROPERTIES OF QUASI-PARTICLES IN POLY(P-PHENYLENE VINYLENE)

We investigate the quasi-particle conformational defects (excitons, po larons and bipolarons) in phenylene vinylene oligomers (PVOs) consisti ng of up to 12 repeat units. The conformations are determined by minim isation of the total Hartree-Fock energy calculated at 3-21G level. Th e Hartree-Fock calculations of the excited states are followed by the CI-Singles calculation. The bond length alternation along the oligomer chain is discussed. On the basis of these results the vibrational tra nsitions are calculated. To correct the basis set truncation error, th e vibrational frequencies are multiplied by a uniform scaling factor. The types of vibrations are assigned. The theoretical spectra are in g ood agreement with the experimental infrared vibrational spectrum of p oly(p-phenylene vinylene) (PPV). (C) 1998 John Wiley & Sons, Ltd.