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  • Atomic, Molecular and Optical Physics  (4)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 13 (1978), S. 483-497 
    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: Le découpage de la densité électronique totale dans une molécule, en contributions provenant des diverses orbitales, permet de définir des régions orbitalaires de caractère conventionnel dont la charge totale est égale à la somme des populations de Mulliken des orbitales constituant les diverses régions. La fluctuation relative de la charge de ces régions s'exprime simplement en fonction des populations de Mulliken et des indices de liaisons. Cette analyse de la densité dans des molécules variées (saturées ou conjuguées) permet de retrouver les liaisons chimiques de la graphie classique comme correspondant à des régions orbitalaires de charge voisine de 2 et présentant une fluctuation relative fiable (≤0, 10). Compte tenu du caractère dynamique que contient la notion de liaison, les résultats obtenus trouveraient une interprétation simple dans l'espace des phases. L'impuissance de la Mécanique quantique de donner une description dans cet espace expliquerait l'impossibilité de déduire de calculs quantiques la notion měme de liaison chimique.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 181-190 
    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 SCF method using localized molecular orbitals which are built up on hybrid atomic orbitals is proposed to obtain the charges in infinite crystals. Hybrid orbitals are built up on a minimal STO basis set. The formalism has been adapted in order to take into account the periodicity of the system and its infinite size by introducing the Madelung constant. The total energy is given by an infinite sum of terms each corresponding to the energy of a bond in the crystal field. Minimizing this bond energy with respect to eigenvectors it is straightforward to obtain the electronic charges, whence the polarity, i.e., the ionicity, of bonds. In this first paper, we study and discuss the polarity of bonds in zincblende and wurtzite-type compounds built up on first and second row elements. Our values are coherent between themselves and in agreement with other authors' results. The connection with electronegativity and polarizability is discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 739-752 
    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 adsorption of one or many silver atoms on a (111) silicon face (reduced to 61 dangling atomic orbitals) is investigated by means of a self-consistent Hartree-Fock method parametrized from atomic and thermodynamical data. The valley sites (above three Si atoms) are favored over the top sites (above one Si atom). The extrapolation of the results obtained for several structures corresponding to the adsorption of n = 1, 2, 3, 4, 6, and 7 Ag atoms allows us to conclude that the most stable structures correspond: for \documentclass{article}\pagestyle{empty}\begin{document}$ \theta = \frac{1}{3} $\end{document} to linear Ag chains (3 × 1 phase), for \documentclass{article}\pagestyle{empty}\begin{document}$ \theta = \frac{2}{3} $\end{document} to an honeycomb lattice (\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt 3 \times \sqrt 3 $\end{document} phase), and for θ = 1 to a centred hexagonal lattice (\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt 3 \times \sqrt 3 $\end{document} phase), the Ag atoms located at the centers of the hexagons being beneath the plan of the hexagons. The adsorption energies corresponding to the various θ are practically equal (ca. 3 eV/Ag). The net charges of Ag atoms are equal to 0.35.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 4
    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: Un procédé de minimisation directe de l'énergie d'une molécule par rapport aux coefficients des orbitales atomiques des fonctions moléculaires est utilisé en vue de déterminer les fonctions de l'état fondamental et des états excités. L'orthogonalité entre les divers états est obtenue par des conditions moins restrictives que celles de Roothaan, si bien que l'énergie obtenue pour la première transition électronique est abaissée: de 0,1 à 0,2 eV pour les transitions π → π* des polyènes.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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