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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 1089-1109 
    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: This is the final paper in a series of three directed toward the evaluation of spin-dependent Hamiltonians. In this paper we derive the reduced matrix elements of the U(2n) generators in a basis symmetry adapted to the subgroup U(n) × U(2) (i.e., spin-orbit basis), for the representations appropriate to many-electron systems. This enables a direct evaluation of the matrix elements of spin-dependent Hamiltonians in the spin-orbit basis. An alternative (indirect) method, which employs the use of U(2n) ↓ U(n) × U(2) subduction coefficients, is also discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 1111-1121 
    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: A treatment for a strong crystal field of cubic symmetry is given using the unitary group approach. Projection operator techniques are utilized to achieve results equivalent to those given recently by Wen Zhenyi.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 1123-1134 
    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: Coupled Hartree-Fock perturbation theory, within the framework of an accurate calculation, has been employed to visualize the electronic current density vector field induced by an external uniform magnetic field in the acetylene molecule. The current regime in a plane containing the molecular axis is rather different from those usually accounted for, evidencing the presence of a toroidal vortex in the C—H bond. The maps are useful in rationalizing the experimentally observed proton and carbon NMR chemical shifts.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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: Previous papers have developed magnetic effective valence bond (EVB) Hamiltonians for the neutral states of π systems; following the same philosophy and using either the quasidegenerate perturbation theory or wave operator formalism, other EVB+ Hamiltonians may be derived for the lowest states of positively charged conjugated hydrocarbons. Their effective operators introduce both charge delocalization (which plays a much more direct role than for the neutral molecules) and effective spin ordering effects. The transferability and efficiency of this EVB+ Hamiltonian are tested by comparison with the exact solutions of the full PPP Hamiltonians. The resulting spectrum is much more dense than in the Koopmans' description; non-Koopmans' states are identified for a few molecules. The applicability of the model to the d bands of metals is discussed in terms of the β/U ratio.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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: Theoretical substituent effects upon the acidity of the title compounds were investigated using STO-3G basis sets augmented by diffuse functions for all oxygen atomic centers of the probe groups. The results are discussed in connection with the available gas-phase data within a novel conception of attractive and repulsive substituent effects.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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: In this paper a detailed study of the structural properties of the three main fractions YI, YII, and Z of clupeine (protamines) has been performed with the aid of nuclear magnetic resonance methods. The investigation includes chemical shift data of protons and C-13 nuclei and measurement of the T1 relaxation times of the C-13 nuclei. These data demonstrate that the flexibility of the three fractions is different and that in the presence of inorganic phosphate fraction YI exhibits structural changes more relevant than the other two fractions. The measurement of the relaxation times, under the assumption of a rigid ellipsoid model, gives an estimate of the rough molecular size of the clupeine fractions. Different side chain mobilities that complement the previous observations based on chemical shift data are determined. A further extension of this work concerns the interaction of the clupeines with natural mononucleotides. An appreciable interaction takes place between fraction YI and purinic nucleotides while a simple electrostatic interaction seems to exist with the other two fractions. A possible explanation of this different behavior seems to involve the formation of large aggregates solely in the case of fraction YI.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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 arrangement of membrane-bound pigments, proteins, and lipids in the thylakoids of higher plants is described, and the role of the membrane in preventing the back-reaction is discussed. The photosynthetic bacterium halobacterium halobium is also described. A simplified quantum-mechanical picture of the primary process in photosynthesis is presented, and the mechanism of electron-hole separation in this picture is compared with the corresponding mechanism in a silicon solar cell. An appendix discusses the application of Frenkel exciton theory to the antenna effect.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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: Usefulness of different Gaussian basis sets for reproducing the “tail” region of the SCF wavefunctions employed in calculations of the exchange-repulsion effect is investigated for the model He-He interaction. It has been shown that extension of the monomer-centered basis set in the scheme of regularized even-tempered basis sets [M. W. Schmidt and K. Ruedenberg, J. Chem. Phys. 71, 3951 (1979)] can be more efficient than augmentation of the fully energy-optimized basis set with diffuse basis functions. It has been also found that Landshoff term vanishes and the “tail” region is well reproduced if monomer wavefunctions are calculated with the basis set of the dimer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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