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  • 11
    Electronic Resource
    Electronic Resource
    Why is the delocalization energy negative and why is it proportional to the number of .pi. electrons (1973)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 95 (1973), S. 8769-8775 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00807a044
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  • 12
    Electronic Resource
    Electronic Resource
    Energy localization of approximate molecular orbitals (1969)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 91 (1969), S. 6864-6866 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01052a064
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  • 13
    Electronic Resource
    Electronic Resource
    Valence states of C2 Feynman's way (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 5205-5215 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Feynman's way is used to calculate total-energy curves for the X 1Σg+, a 3Πu, b 3Σg−, A 1Πu, c 3Σu+, 1 1Δg, 2 1Σg+, d 3Πg, C 1Πg, e 3Πg, D 1Σu+, and C′ 1Πg valence states of C2. Lewis structures are derived for each state. Average (maximum) deviations of calculated spectroscopic constants from experiment are 1.9 (4.3) pm for Re, 18 (32) kJ/mol for De, 12 (36) kJ/mol for Te, 62 (162) cm−1 for ωe, and 16 (31) kJ/mol for asymptotic excitation energies. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475957
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  • 14
    Electronic Resource
    Electronic Resource
    Nondegenerate many-body theory and the treatment of conservation principles (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5847-5849 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Projection operators are used to formulate Lipkin's modified Hamiltonian. By projecting from independent quasiparticle states, a convenient general nondegenerate many-body perturbation theory is generated. A unique feature is that the final results satisfy conservation principles. Practical consequences include ordinary diagrammatic expansions and equations-of-motion for treatments of alternant molecular orbital wave functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451546
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  • 15
    Electronic Resource
    Electronic Resource
    Localized π-orbitals, pauling bond orders, and the origin of aromatic stability (1971)
    Springer
    Theoretical chemistry accounts 22 (1971), S. 196-213 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Energielokalisierte π-Elektronenorbitale für 21 kata- und perikondensierte Kohlenwasserstoffe werden im Rahmen der Hückelschen Näherung angegeben. Es zeigt sich, daß vier verschiedene Arten von ihnen auftreten und daß sich Regeln für ihre Beziehung zu den Paulingschen Bindungsordnungen finden lassen. Die lokalisierte Formulierung erlaubt eine einleuchtende Interpretation der theoretischen Resonanzenergie.
    Abstract: Résumé Obtention d'orbitales de Hückel π localisées selon le critère d'énergie pour 21 hydrocarbures cataet peri-condensés. Donnée des coefficients des orbitales localisées. On trouve quatre types d'orbitales. On donne des règles reliant les orbitales localisées aux indices de liaison de Pauling et une interprétation de l'énergie de résonance théorique est proposée.
    Notes: Abstract Energy-localized π-orbitals are obtained for twenty-one cata- and peri-condensed hydrocarbons in the Hückel approximation. Coefficients for the localized orbitals are given. Four different orbital types are found to occur. Rules are given relating the localized orbitals to Pauling bond orders and an interpretation of the theoretical resonance energy is offered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537628
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  • 16
    Electronic Resource
    Electronic Resource
    Quantum field theoretical methods in chemically bonded systems II (1992)
    Springer
    Theoretical chemistry accounts 84 (1992), S. 1-19 
    Details
    ISSN: 1432-2234
    Keywords: 31.10.+z ; 71.10.+x ; 31.15.+q ; Perturbation theory ; Quasiparticles ; Feynman diagrams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Many-body perturbation theory is derived for chemical bonds. Paired quasiparticles represent the bonds. Products of the paired quasiparticles define a model Bardeen-Cooper-Schrieffer function. The pairing force is added as a model interaction to the self-consistent problem. The starting model is based on valency and adiabatic symmetry correlation. Symmetries are enforced by the model Hamiltonian. Perturbative corrections are expressed as ordinary Feynman diagrams. The number of diagrams needed is the same as for particle-hole theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117400
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  • 17
    Electronic Resource
    Electronic Resource
    Quantum field theoretical methods in chemically bonded systems IV (1992)
    Springer
    Theoretical chemistry accounts 84 (1992), S. 37-53 
    Details
    ISSN: 1432-2234
    Keywords: Perturbative methods ; Perturbative analysis curves ; H2 ; LiH ; FH ; F2 ; Single bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new perturbative procedure is analyzed numerically for four single bonded diatomic molecules. The starting model is the second-quantized self-consistent Heitler-London model. The unperturbed function is a four-determinant Bardeen-Cooper-Schrieffer function. The model Hamiltonian is the ordinary Hamiltonian plus linear and quadratic powers of a two-level number operator. Parameters which multiply the additional terms are chosen to enforce particle-number symmetry. Convergence of the perturbative series for the energy as a function of internuclear distance is reasonable: third-order corrections are about an order of magnitude smaller than second-order corrections; total corrections through third order are about two orders of magnitude smaller than first-order energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117402
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  • 18
    Electronic Resource
    Electronic Resource
    Quantum field theoretical methods in chemically bonded systems III (1992)
    Springer
    Theoretical chemistry accounts 84 (1992), S. 21-35 
    Details
    ISSN: 1432-2234
    Keywords: 31.10.+z ; 71.10.+x ; 31.15.+q ; Perturbative methods ; Potential energy curves ; H2 ; LiH ; FH ; F2 ; Single bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new perturbative method is applied to single bonds. The starting model is the second-quantized self-consistent Heitler-London model. The unperturbed function is a four-determinant Bardeen-Cooper-Schrieffer function. Perturbative corrections are computed with renormalized Feynman diagrams. Convergence is satisfactory by third order. Calculated (experimental) dissociation energies in eV are 4.61 (4.75) for H2, 2.37 (2.52) for LiH, 6.22 (6.13) for FH, and 1.88 (1.66) for F2. Calculated (experimental) equilibrium bond distances in Å are 0.739 (0.741) for H2, 1.598 (1.596) for LiH, 0.903 (0.917) for FH, and 1.395 (1.412) for F2. Calculated (experimental) vibrational frequencies in cm−1 are 4578 (4401) for H2, 1396 (1406) for LiH, 4447 (4138) for FH, and 927 (916) for F2. Other spectroscopic constants agree with experiment to within 11% except for anharmonicities which differ from experiment by up to 20%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117401
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  • 19
    Electronic Resource
    Electronic Resource
    Localized charge distributions (1975)
    Springer
    Theoretical chemistry accounts 37 (1975), S. 177-216 
    Details
    ISSN: 1432-2234
    Keywords: Localized charge distributions ; Acyclic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A localized molecular orbital has been found to extend slightly and regularly into regions away from the chemical bond which contains most of its charge cloud. This was made the basis for a method of transferring localized orbitals among similar molecules. Each localized orbital induces a set of so-called molecule invariant fragments consisting of one bond fragment and collections of geminal fragments, vicinal fragments, and third and fourth neighbor fragments. Localized orbital expansion coefficients in a hybrid basis can be calculated for these molecule invariant fragments without solving any equations or performing any laborious computations. The present work is an application to acylic hydrocarbons. The results are based on the analysis of 33 INDO-SCF molecular orbital wavefunctions in the localized representation. Computational methods for obtaining close approximations to localized orbitals are also discussed. The application of a suggested pseudo-eigenvalue localization method and its accompanying self-consistent iteration process are found to not converge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548090
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  • 20
    Electronic Resource
    Electronic Resource
    Theoretical studies of atmospheric molecules: SCF and correlated energy levels for the NO2, NO 2 + and NO 2 − systems (1977)
    Springer
    Theoretical chemistry accounts 46 (1977), S. 183-189 
    Details
    ISSN: 1432-2234
    Keywords: NO2, NO 2 + , and NO 2 − , SCF and MC-SCF/CI calculations of ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract SCF and MC-SCF/CI calculations were carried out on the low-lying electronic states of NO2, NO 2 + and NO 2 − , using a double-zeta quality basis set of contracted Gaussian functions. The calculations were performed primarily at the equilibrium geometry (R NO = 2.25 ao, θONO=134 °) of theX 2 A 1 state of NO2. SCF calculations on NO 2 + in a linear conformation were also performed. Results are presented and compared with experiment and other calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00578228
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