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  • 1
    Electronic Resource
    Electronic Resource
    A Monte Carlo-quantum mechanics study of the solvatochromic shifts of the lowest transition of benzene (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9874-9880 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We examine the spectroscopic red shifts that occur when benzene is dissolved in (liquid) benzene, in cyclohexane, in carbon tetrachloride, and in water. For this we develop a mixed classical/quantum model in which uncorrelated structures are obtained from Monte Carlo simulation, and these structures are then used for quantum chemical calculations including the chromophore and all solvent molecules within the first radial distribution maxima. We discuss the effects of different sampling techniques and the inclusion of more, or less, solvent molecules in the quantum chemical supermolecule calculation. We obtain shifts of −306 cm−1, −268 cm−1, −456 cm−1, and −122 cm−1, in excellent agreement with the experimentally observed shifts of −332 cm−1, −308 cm−1, −458 cm−1, and −143 cm−1, respectively. We note that the larger shift observed in carbon tetrachloride that is not expected on the basis of larger dielectric constant results from small contributions of the charge transfer type from solvent to solute. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481624
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  • 2
    Electronic Resource
    Electronic Resource
    Including dispersion in configuration interaction-singles calculations for the spectroscopy of chromophores in solution (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 7293-7299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we prove that a configuration interaction electronic structure calculation on a supermolecule that contains only single excitations includes dispersion interactions between the two subsystems when energy differences are taken between the Hartree–Fock (molecular orbital) ground state and low energy excited states in which single excitations dominate. This theorem is proven up to second order in perturbation theory. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481332
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical interpretation of the absorption and ionization spectra of the paracyclophanes (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 2114-2120 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00162a011
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  • 4
    Electronic Resource
    Electronic Resource
    Extreme electron correlation effects on the electric properties of atomic anionsThis work was supported by CNPq and FAPESP (Brazil). (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 265-270 
    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 contribution of the electron correlation effects to the calculated dipole polarizability and hyper-polarizability of the first-row atomic anions is calculated and analyzed. It is shown that the total correlation contribution to the dipole hyperpolarizability is extremely large with the Hartree-Fock model accounting for only a small fraction of the accurate result. The linear and, more pronounced, the nonlinear response of atomic anions to the application of an electric field emphatically shows the effects of the correlated motion of the electrons. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520828
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  • 5
    Electronic Resource
    Electronic Resource
    Sampling configurations in Monte Carlo simulations for quantum mechanical studies of solvent effects (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 66 (1998), S. 249-253 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Discrete models obtained from computer simulation are in increase use to study solvent effects. The approach consists of generating supermolecular structures for quantum mechanical calculations. The properties of the solute are calculated as an ensemble average over configurations generated by the simulation. An analysis of the efficiency of the simulation shows that the number of configurations necessary for the ensemble average can be reduced drastically. As an application to solvatochromism, the calculated spectral shift of the 1B2u(π - π*) transition of benzene in water is shown to be the same whether it is calculated with many but correlated configurations or with just a few uncorrelated configurations.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 249-253, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Structure dependence of the low-lying excited states and the first dipole hyperpolarizability of phenol blue (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 745-750 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (CH3)2NC6H4NC6H4O is a merocyanine dye that exists in resonance between the two extreme conformations of a keto and an eno form. The keto form is more stable in the gas phase and the eno form is believed to be more stable in solution. We show that the keto form can prevail in nonpolar solvents, but in polar solvents like chloroform, the eno form should be dominant. Analysis is made of the solvent effects in the low-lying absorption transition and its consequence in the first dipole hyperpolarizability. We show by explicit calculations that the hyperpolarizability of the eno form is one order of magnitude greater than in the keto form. We then contend that this structure dependence may also lead to very large changes of the hyperpolarizability of similar molecules and polymers in solvents.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 745-750, 1998
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Electron correlation effects on the angular momentum anisotropies of the dipole polarizabilities of the first-row stable atomic anions (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 459-463 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dipole polarizabilities of B-(3P) and O-(2P) are calculated using large basis sets and inclusion of high-order electron correlation effects. Special attention is given to the anisotropies derived from the different components of the orbital angular momentum |ML| = 1, 0. A very large influence of the results on electron correlation is found. This influence is larger for the |ML| = 1 component. However, whereas for B- no low-order level gives acceptable results, for O- due to cancellation effects, MBPT (4), and even MBPT (2), approximate the highest-level [CCSD(T)] result. Our best results are 463.1 and 400.3 au for the average and anisotropic polarizabilities of B-. For O-, these numbers are 37.7, and 22.2 au, respectively. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 459-463, 1997
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Calculation of the absorption spectrum of benzene in condensed phase. A study of the solvent effects (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 885-891 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The red shift of the first absorption band of benzene in the condensed phase is calculated. The solid-phase calculations are performed using the experimental crystal structure. For the liquid two different approaches are considered. One is the herringbone structure suggested by X-ray experiments, and the other uses supermolecules generated by Monte Carlo simulation. Attention is given to the contribution of the usual parallel and T-shape conformations of the benzene dimers obtained in the simulation. Comparison with experiment shows a relatively poor result for the herringbone structure and good agreement for the supermolecular structures generated by the simulation.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 885-891, 1997
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    A comparison of different many-body perturbation theory calculations of the ground state of SiS (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 395-401 
    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: A comparison of different many-body perturbation theory (MBPT) calculations of the ground state rotational and vibrational constants of SiS is made. The calculations are performed up to the complete fourth-order MBPT level, and in all cases two basis sets are utilized. The results of the third-order and some incomplete fourth-order calculations are in good agreement, but the complete fourth-order is among the worst as compared with the experimental data. Analysis of the different contributions to the calculated correlation eneriges points towards the necessity of including even higher-order terms of the(MBPT) expansion.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560330503
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  • 10
    Electronic Resource
    Electronic Resource
    Continuum contribution to polarizabilities and scaling (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 16 (1979), S. 985-991 
    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 role of the continuum, so important in ground-state properties, is known to be less important and may even be negligible in the computation of polarizabilities and other higher negative moments of the oscillator strength distribution. This can be rationalized in terms of the solutions of the inhomogeneous equation generating the moments as an alternative to the dominating first term in an eigenfunction expansion. This leads in a natural form to the approximation Fφ0(1 + w(r)) for the perturbed wave function where 1 + w(r) represents a nonuniform scaling of the unperturbed function φ0.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560160505
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