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  • 1965-1969  (26)
  • 1850-1859
  • Computational Chemistry and Molecular Modeling  (26)
  • 1
    Electronic Resource
    Electronic Resource
    Two-particle density functions for a spin-projected single Slater determinant (1967)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 1 (1967), S. 421-425 
    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
    Description / Table of Contents: On a calculé, pour un déterminant de Slater projeté sur un sous-espace de spin défini, les fonctions de densité pour deux électrons, définies par McWeeny.
    Abstract: Die Zweielektronenfunktionen von McWeeny, sind für eine Spin-projizierte Slaterdeterminante berechnet worden.
    Notes: The two-particle density functions introduced by McWeeny are calculated for a spin-projected Slater determinant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560010414
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  • 2
    Electronic Resource
    Electronic Resource
    On the least squares procedure for atomic calculations (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 169-184 
    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 discuss the properties of one version of the least squares (LS) method for the solution of the Schrödinger equation. These properties are exemplified by a number of calculations on the n1S and n3S states of helium, up to principal quantum number three, which are very much more accurate than previous LS calculations on helium. Particular attention is paid to the convergence properties of the LS procedure and we compare it with the simpler Rayleigh-Ritz (RR) procedure in the case when the RR matrix elements are evaluated numerically over the same quadrature mesh as used in the LS procedure. We conclude that although the LS procedure is capable of high accuracy it has no advantages which would justify its sole use in place of the RR procedure. However, it does have some advantages when used in conjunction with RR, in that it gives an estimate of the numerical accuracy of the RR energies.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030203
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The density matrix in the two-particle function method (1967)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 1 (1967), S. 675-692 
    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
    Description / Table of Contents: Les matrices de densité du premier et du second ordre D(N) et D2(N) pour la fonction g(n) = AN[g(1, 2) … g(N - 1, N)] sont emprimées par la fonction même g(1, 2) et par sa matrice de densité D. Dans l'état singulet les fonctions génératices pour les parties spatiales sont simplement liées à la résolvante de l'équation de Fredholm dans laquelle la partie spatiale D sert de noyau. Quelques cas particuliers de g(1, 2) sont considérés. On établit que le nombre de grandes valeurs propres D2(N) ne dépasse pas le nombre de valeurs propres différentes de D. Ainsi c'est la perturbation dans le spectre D qui produit ces grandes valeurs propres.
    Abstract: Die Dichtematrizen der ersten und zweiten Ordnung D(N) und D2(N) für die Funktion g(n) = AN[g(1, 2) … g(N - 1, N)] werden durch die Funktion g allein und ihre Dichtematgrix erster Ordnung D ausgedrückt. Im Singletzustand hangen die erzeugenden Funktionen für die räumlichen Teile dieser Matrizen mit dem Resolventum von Fredholms Gleichung, mit dem räumlichen Teil von D als Kern zusammen. Hier werden einige spezielle Fälle für g(1, 2) betrachtet. Es wurde festgestellt, dass die Zahl der grossen Eigenwerete D2(N) Die Zahl der verschiedenen Eigenwerte von D nicht übersteigt. Somit hat die Degeneration im Spektrum D das Auftreten von solchen grossen Eigenwerten zur Folge.
    Notes: The first- and second-order density matrices D(N) and D2(N) for the function g(n) = AN[g(1, 2) … g(N - 1, N)] are expressed by the g function itself and its density matrix D. In a singlet state the generating functions for spatial parts of these matrices are simply connected with there solvent of the Fredholm equation in which the spatial part of D is a kernel. Some special cases of g(1, 2) are considered. It isestablished that the number of large eigenvalues of D2(N) does not exceed that of different eigenvalues of D. Thus the degeneracy in the spectrum of D causes the appearance of such large eigenvalues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560010517
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical study of isoelectronic systems: Diazomethane, ketene and allene (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 1013-1025 
    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: All-electron SCF-LCAO-MO computations for diazomethane, ketene and allene are presented. The basis functions are contracted Gaussian orbitals. Theoretical results are discussed and related to available experimental data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030620
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  • 5
    Electronic Resource
    Electronic Resource
    Accurate variational calculation of upper and lower bounds of dispersion interaction constant of two hydrogen atoms (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 13-15 
    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
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030104
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  • 6
    Electronic Resource
    Electronic Resource
    Laplace transform wave functions (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 1027-1043 
    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 wave function defining a quantum-mechanical system is considered as the Laplace transform of some distribution and the consequent form of the Variational Principle derived; an integral equation defines the eigenfunctions of a certain subclass. The model of the hydrogen-like atom is used to test the theory; the eigenfunctions and associated energy levels of the ground and excited states are obtained for arbitrary values of the orbital quantum number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030621
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  • 7
    Electronic Resource
    Electronic Resource
    23S state of helium (1968)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 2 (1968), S. 333-339 
    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
    Description / Table of Contents: Une méthode qui converge rapidement pour l'état fondamental de l'atome de hélium, a été appliquée aux états excités S. Cette méthode est basée sur un développement de la fonction d'onde en puissances de \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {r_1^2 + r_2^2} $\end{document}, In (r12 + r22), \documentclass{article}\pagestyle{empty}\begin{document}$ w = r_{12} /\sqrt {r_1^2 + r_2^2} $\end{document}. Des charges nucléaires effectives différentes ont été employées pour les deux électrons. Des résultats très satisfaisants ont été obtenus pour les valeurs moyennes de plusieurs opérateurs.
    Abstract: Eine Methode, die sehr schnell für den Grundzustand des Helium-atoms konvergiert, wurde zu den angeregten S-Zuständen ausgedehnt. Diese Methode ist auf eine Entwicklung der Wellenfunktion in Potenzen von \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {r_1^2 + r_2^2} $\end{document}, In (r12 + r22), \documentclass{article}\pagestyle{empty}\begin{document}$ w = r_{12} /\sqrt {r_1^2 + r_2^2} $\end{document} basiert. Verschiedene effektive Kernladungen wurden für die zwei Elektronen benützt. Sehr befriedigende Resultate wurden für die Erwartungswerteverschiedener Operatoren erhalten.
    Notes: A rapidly convergent method, which has previously been applied to the ground state of the helium atom, has been extended to excited S states. This method is based on an expansion of the wave function in powers of \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {r_1^2 + r_2^2} $\end{document}, ln (r12 + r22), \documentclass{article}\pagestyle{empty}\begin{document}$ w = r_{12} /\sqrt {r_1^2 + r_2^2} $\end{document}. Different effective nuclear charges are used for the inner and the outer electrons. Very satisfactory results are obtained for expectation values of various operators.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560020303
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  • 8
    Electronic Resource
    Electronic Resource
    Computation of derivatives for parameter optimization in least-squares fitting of linear combinations of Slater-type orbitals by Gaussians (1968)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 2 (1968), S. 801-805 
    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
    Description / Table of Contents: L'approximation d'une combinaison linéaire des orbitales de Slater en termes de fonctions Gaussiennes est un problème d'optimisation multi-paramétrique. On présente des formules pour l'évaluation du gradient de recouvrement dans un espace paramétrique, et une méthode alternative pour l'évaluation du gradient, qui posséde une application générale. Cette technique permet l'évaluation exacte d'une dérivée sans dérivation et programmation de son expression analytique.
    Abstract: Die Entwicklung der Gaussfunktionen einer Linearkombination von Slaterfunktionen ist eine Optimalisierungsproblem von manchen Parametern. Ausdrücke für die Berechnung des Gradients der Überlappungsintegrale in einem Parameterraum werden hier angegeben. Eine andere Methode der Berechnung des Gradients, die allgemeine Anwendbarkeit besitzt, wird auch beschrieben. Diese Technik lässt die exakte Berechnung einer Ableitung zu, ohne seinen analytischen Ausdruck zu derivieren und programmieren.
    Notes: The approximation of a linear combination of Slater-type orbitals in terms of Gaussian functions is a many-parameter optimization problem. Formulas for computation of the gradient of the overlap in parameter space are reported. An alternative method of computing the gradient is described, which is of general applicability. This technique permits the exact evaluation of a derivative, without derivation and programming of its analytic expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560020607
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  • 9
    Electronic Resource
    Electronic Resource
    Expansion of linear combinations of slater-type orbitals in eigenfunctions of the three-dimensional isotropic harmonic oscillatorThis is the second of a series of papers on the expression of atomic and molecular orbitals in terms of functions related to Gaussians. (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 289-295 
    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: Several classes of functions related to the Gaussian have been used with success as basis sets for the representation of atomic and molecular orbitals.We have compared the representation of a hydrogen 1s orbital by a sum of Gaussian lobe functions with its expansion in eigenfunctions of the three-dimensional isotropic harmonic oscillator. The lobe functions are shown to achieve better expectation values of the energy, with fewer terms. The lobe functions have the further computational advantage of not containing high powers of the radius.It is concluded that the lobe functions are a superior basis set for use in calculations of the electronic structure of atoms and molecules.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030304
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  • 10
    Electronic Resource
    Electronic Resource
    Dimeres composes de molecules dont l'excitation electronique entraine un deplacement de la configuration nucleaire d'equilibre accompagne d'un changement de constante de forceSoumis pour publication à l'International Journal of Quantum Chemistry. (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 377-396 
    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 studied the validity of the traditional model of a dimer that has been treated exactly by Merrifield and Fulton and Gouterman, solving the vibronic coupled equations by a numerical method. This model takes into account the modification of the nuclear equilibrium configuration, but it neglects the variation of the force constant when the monomer is electronically excited from the fundamental to a given excited state (the corresponding electronic potentials are both considered as harmonic). We have shown by inspection of the absorption and fluorescence spectra calculated by solving the vibronic equation exactly that the variation force constant cannot be neglected, even if it is weak, particularly in the weak coupling region. The weak, intermediate and strong coupling criteria have been deduced, for the model studied, by examination of the dimeric electronic potential surfaces for different cases of intermolecular interactions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030402
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