Effect of symmetry lowering on the band structure of polyacetylene

In an attempt to apply band-structure calculations to polymers with “reduced” symmetries, and simultaneously to examine some of the causes of band gaps in semiconducting polymers, two types of symmetry reduction are applied on the all-trans polyacetylene chain. Using a neighboring-segment approximation the consequent perturbations were used to calculate changes to the band structure of the undistorted chain and the energy gaps compared with those obtained from a direct calculation on the distorted polymer.