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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of charge transfer and bond alternation in doped polyacetylene (1981)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 85 (1981), S. 756-758 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150607a006
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical investigations of the aluminum/polythiophene interface (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9144-9153 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Interactions at the interface between aluminum and polythiophene are studied theoretically using ab initio Hartree–Fock and Møller–Plesset perturbation theories as well as semiempirical techniques. Aluminum is found to interact strongly with the polythiophene chain. The fundamental interaction unit corresponds to an aluminum dimer (Al2) bound to a single thiophene ring. This type of interaction strongly modifies the geometrical structure of the polymer chain and induces localization of the π-electron system. The calculated charge transfer between aluminum and the thiophene system is found to be in good agreement with the charge transfer deduced from experimental core level spectra of the aluminum/polythiophene interface. A detailed analysis of the electronic structure, including the correlation effects, of a model system (Al2 interacting with α-trithienylene) is performed. Higher concentrations of aluminum atoms on a polythiophene chain results in the formation of additional Al2–thiophene complexes. Within the first monolayer, clustering of aluminum on polythiophene is shown to be energetically unfavorable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463340
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  • 3
    Electronic Resource
    Electronic Resource
    Towards organic polymers with small intrinsic band gaps. III. Geometric and electronic structures of the base and salt forms of polypyrrylenemethine (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8122-8128 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present semiempirical modified neglect of diatomic overlap (MNDO) geometry optimizations and valence effective Hamiltonian (VEH) pseudopotential band structure calculations on the base and salt (protonated) forms of polypyrrylenemethine. This compound is a conjugated polymer based on 2H-pyrrole rings which are bridged by methine-type carbons. In the base (neutral) form, the band gap is calculated to be 1.47 eV. The presence of imine-type nitrogens results in an electronic structure for polypyrrylenemethine which is significantly different from that of polypyrrole despite the presence of six π electrons per unit cell. After protonation of the imine nitrogens, we find that the band gap for the salt form decreases to 0.78 eV, i.e., a value half as big as that of the neutral form. This strong band gap reduction originates from the geometry modification imposed by the protonation process, which leads to a situation where the pyrrole rings alternate between aromatic-type and quinoid-type geometries. Comparison is made with, on the one hand, the oxidation of polybipyrrolemethenylene, and on the other, the protonation of emeraldine base.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460095
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  • 4
    Electronic Resource
    Electronic Resource
    The poly-3-hexylthiophene/NOPF6 system: A photoelectron spectroscopy study of electronic structural changes induced by the charge transfer in the solid state (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4433-4439 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of poly-3-hexylthiophene (P3HT) is studied in the solid state with photoelectron spectroscopy, as the polymer is gradually doped from NOPF6. Solubility and processability of P3HT allow for the preparation of very clean and very thin films, which are then doped without air-exposure. The evolution of the core level binding energies is related to the modification of the electron density on the conjugated backbone, due to the creation of polaron and bipolaron defects. Upon doping, valence spectra show a shift in the Fermi level of the system, and at saturation doping a finite density of states at the Fermi level is observed unambiguously for the first time in electrically conducting polymers with photoelectron spectroscopy. The experimental data on core and valence levels can be interpreted in terms of the formation of a polaron lattice at high doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458725
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  • 5
    Electronic Resource
    Electronic Resource
    Towards organic polymers with small intrinsic band gaps. II. Investigation of the electronic structure of poly(pyrenylene vinylenes) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1783-1788 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Geometry optimizations and band structure calculations are reported on two polymeric vinylene derivatives of pyrene: poly(1,6-pyrenylene vinylene) and poly(2,7-pyrenylene vinylene). The results are indicative of a dramatic sensitivity of the electronic structure on the mode of connection of the two vinylene units to the pyrene rings, in agreement with the chemist's intuition. An analysis of the atomic π orbital contributions to the one-electron wave functions shows that the HOMO–LUMO characteristics of both compounds are markedly different. The 1-6 mode of connection leads to an electronic structure similar to that of polyparaphenylene with a bandgap of 2.9 eV. The 2-7 mode of connection results in a significantly lower bandgap, around 1.7 eV, due to the stabilization of quinoid resonance structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457083
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic structure of polyisothianaphthene (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4257-4262 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the electronic structure of polyisothianaphthene, comparing the experimental data obtained by x-ray photoelectron spectroscopy (XPS) with the results of valence effective Hamiltonian calculations. In the neutral form, the theoretical density of valence states is in very good agreement with the experimental measurements. The shifts observed for the core and valence levels upon doping confirm the very low value of the band gap in this system. Several models explaining the evolution of the line shapes in the oxidized polymer are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453834
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical studies of the complexes of benzene and pyrene with water and of benzene with formic acid, ammonia, and methane (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7291-7299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present ab initio quantum-chemical calculations including correlation effects via second-order Møller–Plesset perturbation theory, of the structures of the complexes that benzene forms with water, ammonia, methane, and formic acid, and of the pyrene–water complex. We describe our results for a number of complex structures, including symmetric and nonsymmetric configurations, in which the aromatic molecule acts as proton acceptor. In some instances, configurations where benzene is the proton donor are also investigated. Series of calculations are performed in order to assess the energy required for the Lewis acid molecule to move on top of benzene or pyrene. Our results are compared to available experimental data on the geometries and relative binding energies of these complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456207
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  • 8
    Electronic Resource
    Electronic Resource
    Thermochromism in poly(3-hexylthiophene) in the solid state: A spectroscopic study of temperature-dependent conformational defects (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4613-4619 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reversible thermochromism in thin solid films of poly(3-hexylthiophene), or P3HT, has been studied using ultraviolet and x-ray photoelectron spectroscopies (UPS and XPS, respectively). The UPS and XPS spectra, as well as previously published optical absorption spectra, are analyzed using the results of valence effective Hamiltonian (VEH) quantum chemical calculations of the electronic structure of isolated polymer chains. The analysis of the spectra indicates that at elevated temperatures thermally induced electronic localization occurs as a consequence of thermally induced conformational disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454802
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  • 9
    Electronic Resource
    Electronic Resource
    Fine tuning of the band gap in conjugated polymers via control of block copolymer sequences (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2750-2758 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the results of the Austin-Model 1 (AM1) geometry optimizations and valence effective Hamiltonian (VEH) band-structure calculations aimed at determining the evolution of the geometric structure and electronic properties (ionization potentials, electron affinities, band gaps) as a function of unit cell content in two sets of regular block copolymers. The first set consists of poly(p-phenylene vinylene)/poly(2,5-dimethoxy-1, 4-phenylene vinylene) copolymers, the second set of poly(p-phenylene)/polyacetylene copolymers. In the latter case, the band gap can be tuned over the whole visible range, depending on the extent of the block copolymer sequences. Special attention is paid to the possible occurrence of localization phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463065
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  • 10
    Electronic Resource
    Electronic Resource
    Nonlinear optical processes in short polyenes: Configuration interaction description of two-photon absorption and third-harmonic generation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1132-1137 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use a multireference determinant single–double configuration interaction approach within a Pariser–Parr–Pople Hamiltonian (based on long-range hopping integrals and the use of the Ohno formula) to investigate linear polyenes containing from four to sixteen carbons. We calculate the low-lying excited states, the two-photon absorption spectrum, and the third-harmonic generation (THG) response. The mAg state, essential to the cubic nonlinear optical response, is found to saturate as the 6Ag state when chain length increases; for the longer polyenes, another high-lying Ag state also becomes important. We analyze the length dependence of the static third-order susceptibility χ(3); indication of the beginning of saturation behavior is found. Focusing our attention to the two-photon resonance peak present in the free-electron laser THG measurements on polyacetylene, we conclude that the experimental data can be explained within the strongly correlated electron one-dimensional model used in this work, in addition to the weakly interacting model successfully exploited in a previous study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463293
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