Linking model hamiltonians to ab initio and semiempirical methods in descriptions of impurities in conjugated polymers

Abstract

Semiempirical and ab initio electronic structure and model Hamiltonian calculations of the undoped and doped polyacetylene (PA) chain are presented. As a general model Hamiltonian we use the Su-Schrieffer-Heeger (SSH) model combined with the Pariser-Parr-Pople (PPP) model with site-type impurities. More precisely, band gap and charge distributions of a single conducting PA chain bonding with several atomic and molecular radicals as impurities were investigated. From a comparison between the electronic and SSH-PPP calculation it was possible to determine what impurity actually corresponds to the charge distribution obtained with model calculations. Therefore, it is shown within the present results what impurities are being represented in model calculations. This correspondence is fundamental in determining the behavior of molecular circuits and molecular devices. © 2005 Wiley Periodicals, Inc.