Electronic energy-band structure of t r a n s -polyacetylene: EHCO and MNDO studies

Extended Hückel and MNDO programs developed for molecular systems have been modified without reparametrization to perform crystal orbital calculations. A comparison of the qualitative results of these methods with the extended tight binding results of Grant as applied to the band structure calculation of trans-polyacetylene is presented. It is demonstrated that the ETB, EHCO, and MNDO methods give results which show a similar trend with minor differences in detail. The usefulness of the crystal orbital method for the interpretation of experimental density of state curves of doped and undoped polymers is inferred from this study and previous studies on polyethylene.