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  • Electronic Resource  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Ab initio studies of open-shell complexes of CO+ with rare gases (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 436-440 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The open-shell complexes HeCO+, NeCO+, and ArCO+ have been studied using ab initio methods in both the ground and first excited states. Calculations were performed using the 6-311G** and 6-311++G** basis sets with unrestricted Hartree–Fock and Møller–Plesset perturbation theory to fourth order (UMP4). The results predict that all the complexes are bound but that only the Ar species in the ground state is rigid. The most stable equilibrium conformation is linear X–CO+ in the ground state and T-shaped or linear X–OC+ in the first excited state. Observations of these complexes by electronic spectroscopy may be difficult because of the prediction of a geometry change on excitation. The results from several other methods, including restricted open-shell Hartree–Fock with Møller–Plesset, restricted Møller–Plesset for open shells, and quadratic configuration interaction with singles, doubles, and triples, were compared to check that the UMP calculations give a reasonable description of these open-shell molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465767
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  • 2
    Electronic Resource
    Electronic Resource
    Atomic scattering factors for mixed atom sites (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 42-44 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A method is presented for the calculation of analytical coefficients for scattering factors at mixed atom sites. The importance of the concept of compatible coefficients for the separate atoms is stressed and examples of the problems that can arise when trying to find coefficients for mixed atom sites are given. A computer program and its use are described. Two errors in International Tables for X-ray Crystallography [(1974). Vol. IV. Birmingham: Kynoch Press. (Present distributor D. Reidel, Dordrecht)] are noted, for Ru4+ and Bi5+, for which revised coefficients are given. For N, O- and Sr2+ analytical coefficients are given which fit the tabulated scattering factors significantly better than the coefficients in International Tables for X-ray Crystallography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767387099938
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Spin-Projected EHF equations (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 711-722 
    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: Extended Hartree-Fock (EHF) equations are developed for the general open-shell case using a modified pair-orthogonality-constrained variation (POCV) method. The EHF energy is expressed in terms of corresponding orbitals that are required to remain orthogonal and paired for all arbitrary infinitesimal variations.The Euler equations for each set of orbitals are reduced to unique pseudosecular equations, the LCAO form of which may easily be derived. The Euler equations and the expressions obtained for the off-diagonal elements of the ∊γδ (γ, δ = a or b) matrices for the closed-shell case are identical to those obtained by Mayer, who used the generalized Brillouin theorem method. However, the present method yields equations for both closed- and open-shell cases and for any spin state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320609
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    Paper (German National Licenses)
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