A theoretical study of {pi}-conjugated materials
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.
- Research Organization:
- Houston Univ., TX (United States)
- OSTI ID:
- 111263
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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