Investigation of soliton-like excitations in t r a n s-polyacetylene

Abstract

In the study reported here, unrestricted Hartree–Fock calculations were performed on the ground state and several soliton-like defect states of the model large polyene, trans-polyacetylene. The calculations included the use of the random phase approximation to obtain screened electron repulsion integrals and projection of the UHF eigenfunctions to obtain pure spin states. The trans-polyacetylene ground state geometry is characterized here by alternating double and single bonds with lengths of 1.456 and 1.369 Å, respectively. Calculations on model soliton-like defect states yielded functional forms for the bond alternation, spin density, and charge density defects which are consistent with the soliton model for trans-polyacetylene and are similar to those reported elsewhere. The average positive and average negative spin density on chains containing neutral kink defects are 0.045 and −0.011, respectively. These values are in fair agreement with the best experimental estimates of 0.06 and −0.02.