Nonempirical studies of the electronic properties of highly conducting polymers

Abstract

We present ab initio calculations on the electronic structure of highly conducting polymers. A Hartree-Fock study of the lithium doping of all-trans polyacetylene demonstrates that the bond alternation, present in the undoped chain is dramatically reduced as the charge transfer from the lithium atom increases. At ˜0.1e transferred per CH unit, we predict equal bond lengths. The relationship of these results to the soliton model for polyacetylene is discussed. Nonempirical effective Hamiltonian calculations on undoped polyacetylene, polydiacetylene, poly (p-phenylene) and derivatives including poly (p-phenylene sulfide) are described. These calculations provide reliable bandwidths and ionization potentials. The ionization potential results are in good agreement with experimental estimates; the bandwidth results yield a satisfying qualitative correlation to the conductivities obtained on doping for the various systems considered.