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  • 1
    Electronic Resource
    Electronic Resource
    Self-consistent-field iterative transfer perturbation method and its application to the interaction between a polymer and a small molecule (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1147-1152 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An iterative transfer perturbation method is proposed to treat the interaction between a polymer and a small molecule at the level of the ab initio method. The validity of our method is examined by applying it to a simple model system and comparing the results with those from the conventional tight-binding SCF crystal orbital method. The interaction energies and charge distributions obtained are in excellent agreement between the two methods. The present perturbational approach is promising for application to the more complicated interaction between a polymer and impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455221
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  • 2
    Electronic Resource
    Electronic Resource
    Perturbational approach to the interaction between a polymer and a small molecule (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 5727-5734 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The perturbational method developed in the present paper is applied to the interaction between a polymer and a small molecule using a few simple model systems. The validity of our method is studied by comparing the results obtained with the perturbation method and the tight binding SCF crystal orbital method. The total electronic energies and charge distributions obtained are in good agreement with each other for the two methods. This result leads to the conclusion that the present perturbational approach is promising for application to interactions between real polymers and impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449648
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  • 3
    Electronic Resource
    Electronic Resource
    A novel molecular orbital method for the calculations of polymer systems with local aperiodic part: The combination of the elongation method with the supercell method (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2346-2358 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper, we propose a new theoretical approach to treat polymer systems with local aperiodic part efficiently. This approach is the combination of the elongation method with the supercell method which has been developed in our group, and we developed this approach to obtain the electronic structure of a polymer having local aperiodicity by considering the locality of the interaction between periodic and local aperiodic parts. In order to confirm the validity of this method, several model calculations were performed at the complete neglect of differential overlap (CNDO/2) level. That is, we applied this method to all-trans polyacetylene interacting with a small molecule, and to all-trans polyacetylene with partial substitution of hydrogen atoms by fluorine atoms. We compared the results obtained by this calculation with those obtained by usual crystal orbital calculation concerning total energy, computational time, and electron density distribution. The charge extension on the polymer chain under the influence of aperiodicity was also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466481
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  • 4
    Electronic Resource
    Electronic Resource
    An efficient cluster elongation method in density functional theory and its application to poly-hydrogen-bonding molecules (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 10808-10823 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The elongation method to synthesize the electronic states of polymers is developed at the level of the density functional theory using the linear combination of Gaussian-type orbitals local spin density method. In this treatment, the interactions between the localized molecular orbitals of a cluster and the canonical molecular orbitals of an attacking monomer are successively included, where the Kohn–Sham equation is self-consistently solved instead of the Hartree–Fock equation in the conventional ab initio method. In the process of the cluster extension, an efficient treatment is implemented to calculate the matrix elements of Coulomb integral and exchange-correlation potential. The reliability and the efficiency of this method are examined via applications to hydrogen molecule cluster, linear water cluster (H2O)n and formamide cluster (CHONHH2)n. It was shown that the present method saves significantly the computational time and disk storage in the large cluster calculations, and provides good agreements with the results by the conventional density functional treatment for the whole system. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468479
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  • 5
    Electronic Resource
    Electronic Resource
    Calculations of the excitation energies of all-trans and 11,12s-dicis retinals using localized molecular orbitals obtained by the elongation method (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 3569-3575 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the present article, the excitation energies of the all-trans and the 11,12s-dicis retinals were calculated by using the elongation method. The geometries of these molecules were optimized with the 4-31G basis set by using the GAUSSIAN 92 program. The wave functions for the calculation of the excitation energies were obtained with CNDO/S approximation by the elongation method, which enables us to analyze electronic structures of aperiodic polymers in terms of the exciton-type local excitation and the charge transfer-type excitation. The excitation energies were calculated by using the single excitation configuration interaction (SECI) on the basis of localized molecular orbitals (LMOs). The LMOs were obtained in the process of the elongation method. The configuration interaction (CI) matrices were diagonalized by Davidson's method. The calculated results were in good agreement with the experimental data for absorption spectra. In order to consider the isomerization path from 11,12s-dicis to all-trans retinals, the barriers to the rotations about C11–C12 double and C12–C13 single bonds were evaluated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474696
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  • 6
    Electronic Resource
    Electronic Resource
    Calculations of phase transition of polydiacetylenes using localized molecular orbitals by elongation method (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 10303-10308 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoinduced phase transition models between two distinct structures (acetylene and butatriene types) of polydiacetylene were investigated by using an elongation method. The geometries of these oligomers were optimized with ab initio self-consistent field. The wave functions for the calculation of the excitation energies were obtained with complete neglect of differential overlap in spectroscopy (CNDO/S approximation) by the elongation method. The excitation energies were calculated by using the single excitation configuration interaction method on the basis of localized molecular orbitals. The energy diagram for the phase transition is plotted and the structural change associated with the photoinduced excitation is discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476491
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  • 7
    Electronic Resource
    Electronic Resource
    An analytical Hückel-type approach to the relationship between Peierls instability in polyenes and interchain interaction (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 9726-9737 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We propose a convenient method to estimate the magnitude of Peierls instability in finite one- and two-dimensional (1D and 2D) polyenes from the view point of orbital symmetry. The formulas are derived in terms of in-phase and out-of-phase interactions between adjacent carbon atoms on the basis of the analytical Hückel orbitals for polyene with an arbitrary length. The stabilization energies due to bond alternation are defined for the individual energy levels. It is visually shown that bond alternation gives rise to stabilizing the occupied orbitals and destabilizing the vacant orbitals without using the k space based on periodic boundary condition in infinite polymer. This treatment is further extended to the Peierls instability in 2D polyene on the basis of the analytical Hückel orbitals derived for its regular structure. Total π and σ energies are provided as functions of bond alternation and interchain interaction. It is demonstrated that bond alternation is strongly suppressed under the existence of interchain interaction, in which interchange between occupied and unoccupied orbitals plays a crucial role. This treatment would provide a first step to investigate the relationship between crystal structure of more complicated polymer and its electronic property in connection with interchain interaction. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469936
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  • 8
    Electronic Resource
    Electronic Resource
    Local density of states of aperiodic polymers using the localized orbitals from an ab initio elongation method (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8432-8440 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An elongation method, which was already proposed to calculate efficiently the electronic states of aperiodic polymers, is developed to provide the local density of states. Elongation method is carried out by repeating the uniform localization of wave functions with inclusion of the interaction between the cluster and an attacking molecule. At first, we develop this method to the ab initio level. Next, we show that the local density of states (LDOS) is obtained efficiently following the elongation step without treating the whole system directly. The validity of our method is examined via application to a hydrogen molecule cluster by comparing the results with those by the conventional ab initio method for the whole system. This approach makes it possible to investigate the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and their density of states on each site of a polymer chain, which will provide a novel approach to examine intra- and intermolecular reactivities within and between aperiodic polymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463413
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  • 9
    Electronic Resource
    Electronic Resource
    A theoretical synthesis of polymers by using uniform localization of molecular orbitals: Proposal of an elongation method (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5419-5431 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The elongation method, a new approach to calculating the electronic structure of polymers efficiently, is proposed as a model for real polymerization reactions following the normal chain reaction processes of initiation, propagation, and termination. The calculations are carried out by repeating the uniform localization of wave functions with inclusion of the interaction between the end group of the cluster and an attacking molecule. As a first step of this treatment, the validity of our method is examined via application to regular and irregular model polymers consisting of hydrogen molecules at the extended Hückel level and comparing the results with those obtained from the conventional variational method. Furthermore, this treatment is performed on the real polymers such as polyethylene and polypropylene stereoisomers, and is proved to be reliable with advantages in computational time and storage. The approach is promising for application to very large systems on which direct variational calculations of the whole system are impossible. Moreover, it should be emphasized that this approach can mimic real reaction coordinates, or can be considered a theoretical synthesis of polymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461658
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  • 10
    Electronic Resource
    Electronic Resource
    Self-consistent-field variational approach to the interaction between a polymer and a small molecule (1989)
    Springer
    Theoretical chemistry accounts 75 (1989), S. 247-260 
    Details
    ISSN: 1432-2234
    Keywords: Polymer-Impurity ; Ab initio method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A variational SCF treatment based on a perturbational concept is developed and applied to the interaction between trans-polyacetylene and a small molecule. The validity of the present method is examined by comparing the results with those from the conventional tight-binding SCF crystal orbital method. The interaction energies and charge distributions obtained are in good agreement between the two methods. This result suggests that the present variational approach is promising for application to complicated interactions between a polymer and impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00533191
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