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Title: A theoretical study of {pi}-conjugated materials

Abstract

Conducting polymers and fullerenes are {pi}-conjugated materials. In these materials, sp{sup 2} hybridized orbits provide the framework structure, and 2p{sub z} electrons are delocalized and fill the {pi}-electron band partially. Even though the {pi}-band is partially filled, undoped conducting polymers and fullerenes are insulators or semiconductors at best. Actually they have a considerable gap in the {pi}-band because of either electron-photon coupling or the structure. At the same time, their bonds are dimerized in the ground state due to the electron-phonon coupling, which is well explained by the Su-Schrieffer-Heeger (SSH) model Hamiltonian. Besides the electron-phonon coupling, the electron-electron interaction cannot be neglected. Because of the huge dimension of Hilbert space, a complete treatment of electron-electron interaction is impossible. We developed a useful calculational scheme to combine these two effects for the electronic ground state and the lowest excited states. Since the {pi}-band is split and the HOMO-LUMO gap is wide (about 2 eV), the ground state and lowest optically excited states are dominated by the SSH ground state and singlet single excitation (SSE) configurations. In this dissertation, we use either SSH`s independent electron model or SSE calculation to study the electronic properties of conducting polymers and fullerenes. In addition, wemore » study the manifestation of quantum chaos due to the electron-electron interaction from a triplet exciton on a linear molecule.« less

Authors:
Publication Date:
Research Org.:
Houston Univ., TX (United States)
OSTI Identifier:
111263
Resource Type:
Miscellaneous
Resource Relation:
Other Information: TH: Thesis (Ph.D.); PBD: 1993
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; 36 MATERIALS SCIENCE; POLYMERS; ELECTRIC CONDUCTIVITY; ELECTRON-PHONON COUPLING; ELECTRONIC STRUCTURE; FULLERENES; HILBERT SPACE

Citation Formats

Kim, J. A theoretical study of {pi}-conjugated materials. United States: N. p., 1993. Web.
Kim, J. A theoretical study of {pi}-conjugated materials. United States.
Kim, J. 1993. "A theoretical study of {pi}-conjugated materials". United States.
@article{osti_111263,
title = {A theoretical study of {pi}-conjugated materials},
author = {Kim, J},
abstractNote = {Conducting polymers and fullerenes are {pi}-conjugated materials. In these materials, sp{sup 2} hybridized orbits provide the framework structure, and 2p{sub z} electrons are delocalized and fill the {pi}-electron band partially. Even though the {pi}-band is partially filled, undoped conducting polymers and fullerenes are insulators or semiconductors at best. Actually they have a considerable gap in the {pi}-band because of either electron-photon coupling or the structure. At the same time, their bonds are dimerized in the ground state due to the electron-phonon coupling, which is well explained by the Su-Schrieffer-Heeger (SSH) model Hamiltonian. Besides the electron-phonon coupling, the electron-electron interaction cannot be neglected. Because of the huge dimension of Hilbert space, a complete treatment of electron-electron interaction is impossible. We developed a useful calculational scheme to combine these two effects for the electronic ground state and the lowest excited states. Since the {pi}-band is split and the HOMO-LUMO gap is wide (about 2 eV), the ground state and lowest optically excited states are dominated by the SSH ground state and singlet single excitation (SSE) configurations. In this dissertation, we use either SSH`s independent electron model or SSE calculation to study the electronic properties of conducting polymers and fullerenes. In addition, we study the manifestation of quantum chaos due to the electron-electron interaction from a triplet exciton on a linear molecule.},
doi = {},
url = {https://www.osti.gov/biblio/111263}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1993},
month = {12}
}

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