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  • Digitale Medien  (6)
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  • Digitale Medien  (6)
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  • 1
    Digitale Medien
    Digitale Medien
    Reply to the comment on "A proposal for the proper use of pseudopotentials...'' by Igel-Mann and Stoll (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 914-915 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We have shown that there are serious limitations in the use of a one electron pseudopotential to describe the chemisorption of CO on a transition metal. Igel-Mann and Stoll argue that the errors which we identified are due to our use of limited basis sets and to our neglect of corrections for the core–core interaction. We show that these claims are incorrect; a proper analysis of their results provides further support for our conclusions. For the metal–CO interaction, a one electron pseudopotential cannot describe the metal dπ–CO 2π* covalent bonding, an important feature of the interaction, because the d electrons are included in the pseudopotential. Our original conclusions about the requirements for a proper use of these potentials for chemisorption are unchanged.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.449461
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  • 2
    Digitale Medien
    Digitale Medien
    In situ vibrational spectroscopy of specifically adsorbed azide on silver electrodes (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 583-589 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: In situ infrared vibrational spectra of azide ions specifically adsorbed on polycrystalline silver electrodes immersed in aqueous electrolytes of composition 1 to 30 mM azide and 0.1 M perchlorate are reported for the potential range 0.25 to 0 V vs Ag/AgCl (3 M KCl). Adsorbed azide was not detected spectroscopically between 0 and −0.9 V, a range known from differential capacitance measurements to allow adsorption onto the silver electrodes. These experimental observations have been interpreted with the help of ab initio calculations of the vibrational frequencies of [AgN3]0 and [AgN3]− for two configurations with C∞v and C2v symmetries representing simple models for azide adsorbed with its configuration axis perpendicular and parallel to the electrode surface, respectively. Besides the charge states specified, calculations are also reported for static applied fields along the symmetry axis. Taken together, the experiments and calculations support a model in which azide adsorbs oriented perpendicular to the surface at the higher surface concentrations induced by potentials more positive than OV, and is adsorbed with long axis parallel to the surface at negative potentials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.455449
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  • 3
    Digitale Medien
    Digitale Medien
    The nature of the bonding of CN to metals and organic molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2170-2176 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The nature of the bonding of the cyanide ligand to a metal atom and an organic group was examined through a study of the model systems CuCN, CuNC, CH3CN, and CH3NC. These particular molecules encompass extremes of bonding. Three properties of the wave functions are used to characterize the bond: (1) projection of the CN orbitals from the wave function of the complete system; (2) the dipole moment as a function of the distance between CH3 or Cu and CN; and (3) the energetic preference for the CN orientation. These measures show that the CuCN and CuNC bonding is dominantly ionic while the bonding for CH3CN and CH3NC is dominantly covalent. For the CH3 containing molecules, there is participation of the cyanide 2π* orbital in the bond; however, it is not involved in the ionic bond with Cu. In all cases considered, there is a large binding energy between CN and CH3 or Cu; CN can form strong bonds that are of either covalent or ionic character.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.453142
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  • 4
    Digitale Medien
    Digitale Medien
    Spin-Free Quantum Chemistry. XXI. Hartree-Fock theorySupported by the Robert A. Welch Foundation of Houston, Texas. (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 15 (1979), S. 751-767 
    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 theory of the open-and closed-shell restricted Hartree-Fock method is given a unitary group formulation. Both extremum and stability conditions are employed, the former leading to a generalized Brillouin theorem.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560150618
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  • 5
    Digitale Medien
    Digitale Medien
    Spin-Free quantum chemistry. XXII. Multiconfiguration self-consistent field theoryThis work was supported by the robert A. Welch foundation of houston, texas. The paper was presented in part at the third international congress of quantum chemistry (kyoto, october 1979), and at the 1980 sanibel-palm coast symposium (march 1980). (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 861-878 
    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: Second order MCSCF theory is presented in a unitary group formulation for any multiplicity without spin projection. Its reduction to lower order theory is discussed, as well as its extension through the use of effective Hamiltonians.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560200409
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  • 6
    Digitale Medien
    Digitale Medien
    Covalent and ionic contributions to the bonding of atomic and molecular adsorbates on metal surfaces: A cluster model approach (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 675-689 
    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 molecular cluster model approach for the description of processes at surfaces is presented. It involves using finite clusters that contain surface atoms interacting with atomic or molecular adsorbates. Accurate ab initio wave functions can be obtained for the clusters, and, thus, this makes it possible to describe the bonding in terms that are familiar for molecular systems. The adsorbate-substrate interaction can be analyzed by new techniques developed to characterize the bonding as covalent or ionic. This is shown for F on Ag(111) and O and CO on Cu(100) systems. The measures of adsorbate ionicity are (a) the expectation value of a projection operator giving an indication of the number of electrons associated with the adsorbate, (b) the analysis of the dipole moment curve as function of the distance, and (c) the effect of an external electric field on the adsorbate geometry. The consequences of ionic adsorbates on metal surfaces is discussed for two selected topics: adsorption of thiocyanate on Ag electrodes and coadsorption of CO with ionic species.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560380509
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