A NOVEL MOLECULAR-ORBITAL METHOD FOR THE CALCULATIONS OF POLYMER SYSTEMS WITH LOCAL APERIODIC PART - THE COMBINATION OF THE ELONGATION METHOD WITH THE SUPERCELL METHOD

In this paper, we propose-a new theoretical approach to treat polymer systems with local aperiodic part efficiently. This approach is the co mbination of the elongation method with the supercell method which has been developed in our group, and we developed this approach to obtain the electronic structure of a polymer having local aperiodicity by co nsidering the locality of the interaction;between periodic and local a periodic parts. In order to confirm the validity of this method, sever al model calculations were. performed at the complete neglect of diffe rential overlap (CNDO/2) level. That is, we applied this method to all -trans polyacetylene interacting with a small molecule, and to all-tra ns polyacetylene with partial substitution of hydrogen atoms by fluori ne atoms. We compared the results obtained by this calculation with th ose obtained by usual crystal orbital calculation concerning total ene rgy, computational time, and electron density distribution. The charge extension on the polymer chain under the influence of aperiodicity wa s also discussed.