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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 7441-7447 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The first-order exchange energy in the interaction of two helium atoms is expanded as a double-perturbation series with respect to the Moller–Plesset-type fluctuation potentials for the isolated atoms. The resulting perturbation corrections have been calculated using orbital basis sets of varying size. Results in our largest [7s4p2d1f] basis are compared with an accurate value of the first-order energy computed using Gaussian-type geminals. It is shown that the Moller–Plesset-type expansion for the exchange repulsion energy converges moderately fast and that the major part of the intra-atomic correlation correction to the first-order exchange energy is due to one-particle correlation effects included in the Brueckner orbitals.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Numerische Mathematik 58 (1990), S. 109-127 
    ISSN: 0945-3245
    Keywords: AMS(MOS) 65F05 ; 15A09 ; 47B35 ; 93B15 ; CR:G1.3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary Utilizing kernel structure properties a unified construction of Hankel matrix inversion algorithms is presented. Three types of algorithms are obtained: 1)O(n 2) complexity Levinson type, 2)O (n) parallel complexity Schur-type, and 3)O(n log2 n) complexity “asymptotically fast” ones. All algorithms work without additional assumption (like strong nonsingularity).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 50 (1994), S. 353-367 
    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: Single-reference coupled-cluster methods corresponding to various approximate forms of the cluster operator including up to four-electron operators are applied to the simple H4 model system with the aim of numerically studying the attainability and properties of multiple solutions of the systems of nonlinear equations for the cluster amplitudes. Various solutions have been obtained for the excited states 21 A1 and 51 A1. It is documented that there exist nonphysical nonstandard solutions that yield energies very close to the physical ones. A simple way of selecting the physically meaningful solutions is proposed. It is demonstrated that the attainability of nonstandard solutions describing a state of H4 within the framework of a given SE-CC method strongly depends on the cluster structure of that state. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
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