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.

Theoretical investigation of carotenoid ultraviolet spectra

“…The stationary state is fully self consistent with respect to both degrees of freedom, of electrons and bond lengths. We have performed calculations systematically varying the radical parameters from 0 to 1.25 eV [36].…”

In Situ Measure of Intrinsic Bond Strength in Crystalline Structures: Local Vibrational Mode Theory for Periodic Systems

“…The trans- PA system was chosen as an ideal model system, often used in modern organic chemistry textbooks when introducing conjugation and π electron delocalization extrapolating stepwise from ethylene, trans- 1,3-butadiene, etc. , With an increasing number of C 2 H 2 units connected by CC single bonds in a linear chain, the π electron delocalization is expected to enhance and cover more carbon atoms. While various theoretical tools including electron localization function (ELF), localized-orbital locator (LOL), and Mayer bond order have been utilized to study the alternating single–double bonds in conjugated alkenes as isolated molecules, there have been only some scattered investigations on the single and double bond strength in PAs as 1D polymers. − Therefore, we performed a rigorous local mode analysis.…”