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  • Atomic, Molecular and Optical Physics  (3)
  • Theoretical, Physical and Computational Chemistry  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Many-electron-wavepackets method (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1291-1301 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a computational scheme to study the dynamics of many-electrons in molecular systems by wavepackets method. Several approaches to calculation of nonlinear optical properties for molecules under time-independent or time-dependent external electric fields are presented. Some simple examples of one-dimensional two- or three-electron systems are demonstrated concretely. Implications of these results are discussed in relation to the validity of the many electron wavepackets (MEWP) method. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Numerical coupled Liouville approach: Quantum dynamics of linear molecular aggregates under intense electric fields (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 77-87 
    Details
    ISSN: 0020-7608
    Keywords: linear molecular aggregate ; coupled Liouville equation ; hyperpolarizability ; optical retarded field ; optical bistability ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We develop a numerical calculation scheme of a dynamics of the quantum network for linear molecular aggregates under time-dependent electric fields. Each molecule is assumed to be an electric dipole arranged linearly with an arbitrary angle from the longitudinal axis. This approximation is considered to be appropriate for the aggregates with large intermolecular distances and allows us to treat intermediate- and large-size aggregates without enormous direct calculations of the Coulomb interactions. The molecular interactions are taken into account by adding the radiations from these dipoles to the external electric fields. The dynamics is performed by solving the coupled Liouville equation constructed from the Liouville equation for each dipole. The effects of the retarded electric fields are evaluated with numerically exact precision by using the sixth-order Runge-Kutta scheme. As a simple example, we examine the linear aggregates involving two dipoles composed of two-state molecules under the continuous laser fields. The effects of the intensity of external fields, the intermolecular distances, and the angles between the dipole and the longitudinal axis on the population differences are investigated. The linear polarizability spectra are calculated by using the definition of nonperturbative polarizability. An abrupt change like the phase-transition behavior in the variation in the population differences for the applied field intensities is observed for the dimer models. Based on these results, we anticipate the population differences for larger (intermediate)-size aggregates.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 77-87, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Hyperpolarizabilities of one-dimensional Hn systems: Second hyperpolarizability density analyses for regular and charged solitonlike linear chains (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 269-282 
    Details
    ISSN: 0020-7608
    Keywords: hyperpolarizability ; hydrogen chain ; bond alternation ; ab initio ; electron correlation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations of the second hyperpolarizabilities (γ) for one-dimensional hydrogen chains (Hn) with different bond-length alternations and charges are performed. We investigate their signs, magnitudes, and chain-length dependences at various electron correlation levels using an extended basis set. Remarkable differences in the γ are observed for different bond-length alternations and for different charged states. In order to elucidate the differences in γ, spatial contributions of electrons to the γ are analyzed for these short and long Hn chains by using the second hyperpolarizability density plots. The effects of the introduction of charged defects into the linear chains on the γ are also investigated by varying the intercharged defects distance.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 269-282, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Density functional theory without the Born-Oppenheimer approximation and its application (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 659-669 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure for the calculation of molecular properties in the full quantum mechanical treatment is presented. We formulate the non-Born-Oppenheimer density functional theory and propose its numerical scheme. We numerically calculate the energy, particle densities, interparticle distance, and (hyper)polarizability of the hydrogen molecule and its isotopes using this method and discuss isotope effects on the physical properties.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 659-669, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Instability in chemical bonds. II. Theoretical studies of exchange-coupled open-shell systems (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 501-515 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic and geometrical structures of exchange-coupled open-shell systems such as bis(methylene) methane and the chromium-methylene cation were investigated by the molecular orbital and its extended methods: RHF, UHF, UNO-CAS, RMP, UMP, PUMP, APUMP, UCCSD(T), UNO-CI and QCISD(T). The fully optimized geometries of these species by the energy gradients of UMPn solutions are consistent with the experimental values. The total energies of the lowest and highest spin states were calculated in order to elucidate the effective exchange integrals in the Heisenberg model for methylene and bis(methylene) methane. The spin projection is necessary for the UHF-based wavefunctions in the lowest spin state of the species. The binding energies for the chromium cation-methylene double bond were calculated by both spin-unprojected and -projected methods. It was found that the binding energy between Cr+ and 3CH2 by APUHF QCISD(T) is in accord with the experimental value. © 1993 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480848
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  • 6
    Electronic Resource
    Electronic Resource
    Nonadiabatic treatment of molecular systems by the wavepackets method (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1261-1270 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have already developed the many-electron wavepackets (MEWP) method in order to study the dynamics and electronic structure of molecular systems. We extended the MEWP method to study the nonadiabatic effects and formulated a nonadiabatic molecular theory, where both electron and nucleus are treated equivalently. Then we applied our method to the isotope series of hydrogen molecule i.e., H2, HD, and D2, and calculated the total energy and the average distance between nucleus-nucleus, electron-electron, and nucleus-electron in order to analyze numerically the nonadiabatic effect in the molecule. Finally we calculated the real-time evolution of the polarization by means of Chebyshev scheme; and by Fourier transforming this, we found out the excitation spectrum of the system, which corresponds to the electronic excitation and the nuclear vibrational frequency. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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