ON THE STRUCTURE OF BIPOLARONIC DEFECTS IN THIOPHENE OLIGOMERS - A DENSITY-FUNCTIONAL STUDY

The neutral and dication species of thiophene oligomers of increasing size (2 to 12 rings) have been examined and a study made of structural modifications occurring due to the increase in molecular charge; mole cular properties such as charge-density distribution have been calcula ted. Preliminary results concerning the effect of electron correlation included at the density functional theory level are reported. Signifi cant differences with respect to Hartree-Fock results are observed: th e whole bipolaronic defect shape changes so that in the longer oligome rs the bond-length alternation is no longer present. (C) 1998 Elsevier Science S.A.