Optical activities of helical polymers: a crystal orbital theory based on Wannier functions.

In this paper, a novel theory of optical activities for helical polymers has been formulated using crystal orbital methods under periodic boundary conditions. The selection rule of the optical transition was determined in the reciprocal space based on the helical angle of the unit cells. The optical rotatory strength was estimated using Wannier functions, which can be chosen to be real localized orbitals. Contrary to conventional exciton models, the structural parameters of helical polymers can be easily reflected in actual calculations of the optical rotatory strength within the crystal orbital framework. The theory was confirmed by evaluating the optical rotatory strength of a right-handed helical polyacetylene. This approach provides a promising method to evaluate the optical activities of helical polymers with itinerant electrons. [ABSTRACT FROM AUTHOR]