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  • Wiley-Blackwell  (4)
  • 1990-1994  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    The band gap of alternant 1D π-electron systems (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 173-180 
    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: Within the framework of the AMO-EHF approximation for the Hubbard model, it is shown that the band gap ΔE of an arbitrary regular alternant 1D π-system (polymer), having a singlet ground state, is different from zero, i.e., the ground state is a dielectric one. At least one of the three components of the energy gap - the topological, Δtop; the geometrical, Δgeom; or the correlation, Δcorr (combined via the equation ΔE = {Δcorr2 + (Δtop + Δgeom))2}1/2 - is different from zero. Numerical results for several 1D alternant polymers with conjugated π-systems are given. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560510307
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  • 2
    Electronic Resource
    Electronic Resource
    Generation of carbon-cage polyhedra (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 1252-1259 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The problem of the generation of polyhedra with degree-3 vertices, and faces each of which is pentagonal or hexagonal, is addressed in order to characterize carbon in order to characterize clusters of ca. 30 or more atoms. Following Eulerian type arguments such polyhedra are subcategorized in terms of numbers of different types of local structures. An algorithm to generate such polyhedra is developed, and its computer implementation is described. Results for smaller than 80-vertex cages of subcategories anticipated to be more chemically relevant are reported. The singular position of the truncated-icosahedron (buckminsterfullerene) structure is noted.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540121013
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  • 3
    Electronic Resource
    Electronic Resource
    Sixty-atom carbon cages (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 1265-1269 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The enumeration of all 60-atom carbon cages associated to trivalent polyhedra with five-and six-sided faces is addressed. This isomer problem is computationally solved to give 1790 cages, with a further resolution into subclasses of cages with differing numbers p of abutting pairs of pentagonal faces. The individual cages are generated, and then there are computed various graph-theoretic invariants, including Hückel MO energies, HOMO-LUMO gaps, Kekulé structure counts, and conjugated-circuit counts. Associated properties as a function of p are reported and found to be in concert with earlier qualitative arguments. It is found that the most stable of these cages is the unqiue p = 0 Buckminsterfullerene structure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540121015
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  • 4
    Electronic Resource
    Electronic Resource
    Symmetric-group algebraic variational solutions for Heisenberg models at finite temperature (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 43-52 
    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: The Heisenberg spin Hamiltonian for a collection of N spin-1/2 sites is viewed, as favored by Professor Matsen, to be an element of the group algebra of the symmetric group SN. Several computationally tractable, variational group-algebraic approximations for the finite-temperature density matrix are made so as to minimize the Gibb's free-energy functional. Relations to previous quite differently motivated approximations are identified, though improvements are noted with the present approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560410107
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