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  • 1
    Digitale Medien
    Digitale Medien
    On the determination of effective one-electron Hamiltonians to be used for studying large molecules (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 59-70 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We studied the possibility of defining a one-electron effective Hamiltonian in the form of a Hückel-type matrix, taking into account the effect of the environment of the atoms in different molecules (the E2HT). It is found that the appropriate basis set in which this Hamiltonian is defined can be determined by using diatomic fragments. Concerning the matrix elements themselves, the appropriate information can be taken in fragments with a size similar to that of ethane. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560520107
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  • 2
    Digitale Medien
    Digitale Medien
    On the dependence of the energy given by a CI limited to double substitutions with respect to the number of electrons (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 12 (1977), S. 777-779 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560120414
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  • 3
    Digitale Medien
    Digitale Medien
    Relationship between orthogonalization and orbital localization proceduresPresented at the International Symposium of Dalseter (September 2-4, 1976) in honor of the 60th birthday of Prof. P.O. löwdin. (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 12 (1977), S. 579-590 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A condition for the equivalence of the Löwdin orthogonalization method and various localization methods is derived, taking the matrix elements of the localizing operator into consideration. In the example of the π atomic orbitals of benzene, it is shown that the “ultralocalized” functions defined in the Anderson fashion with help of the Boys minimum-fluctuation criterion do not fulfill this condition, in contrast with a Ruedenberg-type localization.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560120316
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  • 4
    Digitale Medien
    Digitale Medien
    Molecular MC-SCF calculations (1970)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 4 (1970), S. 297-313 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A practical method for finding multi-configurational SCF wave functions is proposed. The basic equation is equivalent to the Brillouin theorem; comparison with the usual SCF equations obtained through effective hamiltonians gives an interpretation of the offdiagonal Lagrange multipliers. Numerical applications to Formaldehyde in a minimum Slater-type orbital basis with four different variational wave functions are reported. The molecular orbitals found in these calculations are localized on the chemical bonds. The largest contributions to the energy are obtained from π-π and dispersion-type σ-π correlation.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560040307
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  • 5
    Digitale Medien
    Digitale Medien
    Difficulties in the computation of physical observables due to a truncated CI (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 16 (1979), S. 955-972 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It is proved that the values of various types of physical observables issued from a truncated CI are not size consistent. These observables include electronic transitions, ionization potential, and all the quantities depending on the one-electron density matrix γ. Numerical examples are given. It is found that the error due to this size inconsistency can be important for systems of moderate size (e.g., 16% on a matrix element of γ for a 20-electron system).
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560160503
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  • 6
    Digitale Medien
    Digitale Medien
    Reduced-diabatic vibrational close coupled treatment of molecular dissociation dynamics (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 161-184 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A close coupled treatment in a vibrational adiabatic representation is applied to the study of molecular photodissociation dynamics. The procedure which is developed here involves three steps: transformation from a diabatic to an adiabatic basis set, truncation of the adiabatic basis set, back transformation to a reduced-diabatic basis set. In the two model cases which are studied, dissociation spectra show complicated peaks and dips, patterns interpreted in terms of shape and Feshbach resonances associated to vibrational predissociation with a relatively high potential barrier in the excited state. An important reduction in the number of channels required for a given final accuracy can be reached by using the reduced-diabatic basis set instead of the usual diabatic one. This is very promising for studying energy partitioning in molecular systems with several internal degrees of freedom taking part in the dynamics.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340208
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  • 7
    Digitale Medien
    Digitale Medien
    The N2 problem in molecular CI calculations (1976)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 1061-1070 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The possible existence of spurious terms increasing as the square of the number of electrons is theoretically proved for the CI treatments of molecules limited to single and double excitations, and is revealed by some numerical calculations (alcanes and juxtaposed hydrogen molecules). An improved perturbation scheme is suggested in order to evaluate the CI energy lowering more carefully. Covergence difficulties are found for larger systems (benzene).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560100617
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  • 8
    Digitale Medien
    Digitale Medien
    Perturbation calculation of transition moments in the ArH+ system (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 49-55 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The matrix elements of the transition dipolar momentum IR have been computed between the low-lying states associated to the Lyman-α transition. The orthogonalization of the involved electronic states (obtained by the CIPSI method) has been performed and led to a better value for the asymptotic behavior of the {Ar(3p5, 4s) + H+} configuration. Position of the satellites in the red and blue wing of the line are deduced from the potential-energy curves in the frame of the quasistatic theory.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560180110
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