Comparison of the INDO band structures of polyacetylene, polythiophene, polyfuran, and polypyrrole

The intermediate neglect of differential overlap (INDO) band structures of polythiophene, polyfuran, and polypyrrole are analyzed in terms of the band structure of polyacetylene. This is done by decoupling the INDO Fock operator to obtain the band structure of the carbon system and of the heteroatoms. For all three polymer systems, the highest valence band is essentially a pure carbon band, whereas the lowest conduction band is a strong mixture of carbon and heteroatom bands. This suggests that the electron and hole should show distinct properties. This difference between the electron and hole can be understood in terms of coupling between the respective Wannier functions of polyacetylene and the heteroatoms. Polypyrrole shows a stronger coupling between the carbon and heteroatom bands than polythiophene or polyfuran.