U. Salzner et al., ACCURATE METHOD FOR OBTAINING BAND-GAPS IN CONDUCTING POLYMERS USING A DFT HYBRID APPROACH/, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(15), 1998, pp. 2572-2578
DFT calculations on a series of oligomers have been used to estimate b
and gaps, ionization potentials, electron affinities, and bandwidths f
or polyacetylene, polythiophene, polypyrrole, polythiazole, and a thio
phenethiazole copolymer. Using a slightly modified hybrid functional,
we obtain band gaps within 0.1 eV of experimental solid-state values.
Calculated bond lengths and bond angles for the central ring of sexith
iophene differ by less than 0.026 Angstrom and 0.7 degrees from those
of the sexithiophene crystal structure. IPs and EAs are overestimated
by up to 0.77 eV compared to experimental bulk values. Extrapolated ba
ndwidths agree reasonably well. with bandwidths from band structure ca
lculations.