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  • American Institute of Physics (AIP)  (3)
  • 1
    Electronic Resource
    Electronic Resource
    A localized-basis monoexcited configuration interaction technique for extended systems (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8520-8528 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is demonstrated that the monoexcited configuration interaction matrix, constructed from the localized (or Wannier) orbitals for an one-dimensional extended system with translational symmetry can be used to define a series of finite-dimensional matrices whose lowest eigenvalues and eigenvectors converge to the lowest eigenvalues and eigenvectors of the infinite-dimensional full monoexcited configuration interaction problem. As an illustration, the developed monoexcited configuration interaction approach is applied to the π-electronic model of cyclic polyenes (annulenes) in the framework of the Pariser–Parr–Pople approximation. A standard parametrization scheme has been found to yield a value of ∼2.42 eV for the lowest singlet excitation energy of an infinite polyene, which is in good agreement with the experimental estimate of ∼2 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460085
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Convergence of direct space exchange lattice sums in polymer band structure calculations (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5286-5298 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A study of the convergence properties associated with direct lattice summations of the exchange contributions to the quantities needed in a restricted Hartree–Fock calculation for a polymer, leads to a detailed analysis of the analytic and asymptotic properties of the Fock–Dirac density matrix in the LCAO representation. The results, obtained simply by means of Fourier analysis, provide an important characterization of the restricted Hartree–Fock method as applied to chain-like systems. As a by-product we obtain a general proof in direct space that a partially filled band, which influences drastically the analyticity properties of the density matrix in reciprocal space, leads to a logarithmically diverging derivative of the orbital energy at the Fermi level. This in turn gives a vanishing density of states at that level. This result, well known for the electron gas model, is thus an inherent property of the restricted Hartree–Fock approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451671
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic structure of H2 and HeH+ computed directly in momentum space (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7888-7898 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The possibilities of one-step iterative computations in momentum space previously developed for neutral and charged atoms are now assessed to two-electron diatomic molecular case, the helium hydride positive ion HeH+. The improvements induced in its ground state doubly occupied orbital initially approximated by different primitive Gaussian functions of increasing quality are analyzed through the calculation of test quantities such as the momentum density, 〈p−1〉, 〈p2/2〉, and 〈p4〉. Moreover the structure of the equation leading to the first iterate for HeH+ suggests that the procedure could be generalized to polyatomic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465666
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