STUDY OF INFINITE POLYACETYLENE FROM A HEISENBERG HAMILTONIAN - DIMERIZATION AND LOWEST EXCITATION-ENERGIES

The infinite periodic polyacetylene is studied using a distance-depend ent Heisenberg Hamiltonian extracted from ethylene and a recently prop osed dressed cluster method. The ground state bond alternation is sati sfactorily reproduced. The lowest excitation energies (of triplet and singlet character) are studied as a function of the bond alternation u sing excited roots of the dressed configuration interaction matrix and extrapolation techniques. (C) 1998 Published by Elsevier Science B.V. All rights reserved.