MOLECULAR GEOMETRIES BY THE EXTENDED-HUCKEL MOLECULAR-ORBITAL METHOD III - BAND-STRUCTURE CALCULATIONS

Geometries of extended structures can be evaluated with the extended-Huckel tight-binding method by inclusion of a distance-dependent weighted Wolfsberg-Helmholz formula and an approximate two-body electrostatic repulsive-energy term. We explain the theoretical procedure which is shown to be straightforward. Application to (all-trans)-polyacetylene yields alternating C,C bond lengths and a bandgap of 1.6 eV at the optimized geometry, in good agreement with the experimental finding.