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  • 1
    Electronic Resource
    Electronic Resource
    Direct Enthalpimetry. A New Thermochemical Approach to Quantitative Analysis. (1964)
    s.l. : American Chemical Society
    Analytical chemistry 36 (1964), S. 2131-2133 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60217a030
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  • 2
    Electronic Resource
    Electronic Resource
    Moisture Determination with Karl Fischer Reagent Utilizing an Enthalpimetric Temperature Pulse. (1966)
    s.l. : American Chemical Society
    Analytical chemistry 38 (1966), S. 1750-1751 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60244a002
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Hartree-Fock values of some atomic integrals useful in simplified LCAO-MO calculations for molecules - I. Atoms B, C, N, O, F
    Amsterdam : Elsevier
    Atomic Data and Nuclear Data Tables 23 (1979), S. 535-545 
    Details
    ISSN: 0092-640X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0092-640X(79)90029-9
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  • 4
    Electronic Resource
    Electronic Resource
    Cluster relations for multireference coupled-cluster theories: A model study (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3549-3561 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The validity of various coupled-cluster conditions, that were recently formulated for both the valence-universal open-shell coupled-cluster theory based on Lindgren's exponential ansatz and the state-universal theory employing the Jeziorski–Monkhorst ansatz, are examined for two model systems consisting of two and four slightly stretched, interacting hydrogen molecules. These cluster conditions ascertain the possibility to represent four-electron terms in the wave operator through appropriate products of two-electron terms and thus justify the truncation of the open-shell cluster operators employed to at most two-electron terms. A single parameter that determines the geometry of the studied model systems makes it possible to continuously vary the extent of quasidegeneracy between the two lowest energy states over a wide range. It is shown that the cluster conditions are relatively well satisfied only in the strongly quasidegenerate region, except for a few very small amplitudes whose effect on the resulting energies should be insignificant. To assess the validity of the often made assumption of negligibility of one-electron amplitudes, the generalized cluster conditions involving these terms were also examined. The role played by these additional terms was shown to be small. Finally, in the valence-universal case, the role of orbital choice was also investigated by performing cluster analysis with both system and core spin orbitals. The effect of using different orbital alternatives was again found to be small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460857
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  • 5
    Electronic Resource
    Electronic Resource
    Stationary points on the lowest doublet and quartet hypersurfaces of the N3 radical: A comparison of molecular orbital and density functional approaches (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10969-10982 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Stationary points on the doublet and quartet hypersurfaces of the N3 system are studied using the single-configurational and multi-configurational Hartree–Fock approaches and the methods which include the dynamic correlation effects on a perturbational way or through the density functional theory (DFT). A general structure of both the hypersurfaces within the C2v symmetry is explained on the basis of the Walsh diagram and studied by a simplified configuration interaction (CI) based on a small complete active space (CAS) of five valence orbitals. The minima found in this way are studied in detail by the other methods mentioned above without the symmetry constraints. The stability of minima and existence of energetic barriers are explained by the changes of the bonding — antibonding character of some valence orbitals, observed in the Walsh diagrams for both the orbital and the Kohn–Sham energies. All the methods applied indicate, that a stable ring N3 conformer should exist with the 2B1 ground state. Alternative mechanisms for a deactivation of the linear excited states of N3 are proposed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472865
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  • 6
    Electronic Resource
    Electronic Resource
    Accurate MR CI studies of the N"2 ground state
    Amsterdam : Elsevier
    Chemical Physics 111 (1987), S. 265-269 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(87)80139-8
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio SCF study of some low-lying electronic states of the H"2O molecule, NH"2 radical and their mono-positive ions
    Amsterdam : Elsevier
    Journal of Molecular Structure 52 (1979), S. 281-291 
    Details
    ISSN: 0022-2860
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-2860(79)80125-8
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  • 8
    Electronic Resource
    Electronic Resource
    Thermoanalytical investigation of mixtures containing oxalic acid, sodium hydrogen oxalate and sodium oxalate (1980)
    Springer
    Journal of thermal analysis and calorimetry 18 (1980), S. 57-63 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Résumé On a étudié le système ternaire contenant H2C2O4 · 2H2O, NaHC2O4 · H2O et Na2C2O4. On a établi que les courbes thermiques des mélanges ne correspondaient pas à la somme algébrique de leurs courbes composantes. On a interprété toutes les étapes de la décomposition thermique et donné les moyens d'effectuer des analyses qualitatives et quantitatives du système.
    Abstract: Zusammenfassung Das H2C2O4 · 2 H2O, NaHC2O4 · H2O und Na2C2O4 enthaltende ternäre System wurde untersucht. Es wurde festgestellt, daß die thermischen Kurven der Gemische nicht den algebraischen Summen ihrer Komponentenkurven entsprachen. Sämtliche Stufen der thermischen Zersetzung wurden zugeordnet und die Möglichkeiten der Durchführung qualitativer und quantitativer Analysen im System angegeben.
    Notes: Abstract The ternary system containing H2C2O4 · 2H2O, NaHC2O4 · and Na2C2O4 was investigated. It was ascertained that the termal curves of the mixtures were not the algebraic sums of their component curves. All thermal decomposition stages were interpreted and the means of performing qualitative and quantitative analyses in the system were given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01909453
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  • 9
    Electronic Resource
    Electronic Resource
    Modified virtual orbitals (MVO) in limited CI calculations (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 649-656 
    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 modification of virtual orbitals seems to be an inexpensive way of calculating a large part of the correlation energy. Three types of MVOS have been compared in this paper, on the basis of limited valence-shell CI calculations for some lower states of the H2O molecule: A  -  orthogonalized eigenfunctions of exchange operators; B  -  eigenfunctions of one combined exchange operator; C  -  eigenfunctions of the Fock operator for a highly ionized system. For small virtual spaces (20% of available orbitals used), approach C gives 70% of EcorrCI-SD, being superior to the two other approaches. When using only 50% of MVOS, all the three types of approaches result in calculating 90% of EcorrCI-SD, but the ionic orbitals give a better description of the state separations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560390502
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  • 10
    Electronic Resource
    Electronic Resource
    A coupled-cluster method for quasidegenerate states (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 535-557 
    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 size-extensive, multireferences coupled-cluster method for studies of quasidegenerate states based on the Jeziorski-Monkhorst [16] ansatz for the cluster operator (Ω = ∑eTjPj, where the sum is extended over the configurations spanning the model space), is presented and applied in pilot calculations. The method is referred to as multireference coupled electron-pair method (MR CEPM), because it is assumed that the individual cluster operators can be approximated by their two-body parts, i.e., Tj ≈ Tj(2). The linear version of this method (MR L-CEPM) is also discussed. Both methods are applied to two simple model systems: (1) a minimum basis set model involving eight hydrogen atoms in various spacial arrangements for which the degree of quasidegeneracy can be continuously varied; (2) a model involving the C2ν insertion of Be into H2. For the first time in multireference coupled-cluster calculations, the nonlinear parts of the equations are completely accounted for. The MR CEPM results are very encouraging for strongly quasidegenerate states. The MR L-CEPM results are slightly below the accurate (FCI) values.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340607
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