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  • 1
    Electronic Resource
    Electronic Resource
    An improved molecular orbital localization scheme
    Amsterdam : Elsevier
    Computers and Chemistry 15 (1991), S. 115-119 
    Details
    ISSN: 0097-8485
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0097-8485(91)80035-K
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Adatom-based (2 x 2n) reconstruction on Ge(111)
    Amsterdam : Elsevier
    Surface Science Letters 241 (1991), S. A6 
    Details
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0167-2584(91)91062-2
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Adatom-based (2 x 2n) reconstruction on Ge(111)
    Amsterdam : Elsevier
    Surface Science 241 (1991), S. 135-145 
    Details
    ISSN: 0039-6028
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0039-6028(91)90218-H
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Site occupancy and molecular complex formation of 19F ions in fullerenes C60 and C70 studied by TDPAD (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 557-562 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract TDPAD spectroscopy measurements have been performed on two fullerene samples, C60 and C70, with recoil implanted 19F ions as probe nuclei. Quadrupole coupling frequencies of νQ= 54(1) MHz for C60 and νQ= 57(1) MHz for C70 were observed. These frequencies are associated with a C–F molecular complex formation. The C70 sample was also examined for possible effects due to variation of temperature. No significant changes were observed. An additional frequency of νQ= 13(1) MHz registered for both samples has to be attributed to the formation of H–F complexes. Finally, both samples were analysed for proton dose dependent effects, due to the (p,p'γ) implantation process but no effects have shown up. Specifically, computational studies based on quantum chemical methods were performed to assist in the interpretation of the experimental results, using the code MOPAC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017090632452
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Extrapolation of real-space quantum chemical calculations from finite-size super cells to the ideal infinite system. II. Application to one-dimensional polymers (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1287-1299 
    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: Calculations of finite atomic clusters based on the Hartree-Fock self-consistent field theory are modified to model more closely the ideal behavior of the infinite system. The density matrix of the standard finite supercell calculation is extrapolated to an infinite supercell so that it contains information from a continuum of k points in the first Brillouin zone. This modification is incorporated into the self-consistency loop of the MOPAC quantum chemistry program and leads to improved results compared to a standard finite supercell calculation. Heats of formation, bond lenghts, and electronic properties converge more quickly to the correct ground-state values. For polyacetylene, we obtain a reduced bond-length alternation of Δr = 0.084 Å, which is in agreement with more sophisticated calculations containing electron correlation effects. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520605
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  • 6
    Electronic Resource
    Electronic Resource
    Extrapolation of real-space quantum chemical calculations from finite-size super cells to the ideal infinite system. I. Theory (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1273-1285 
    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: A method is proposed how to calculate the correct density matrix of an infinite polymeric chain from that of a standard finite supercell calculation. The density matrix of the finite supercell is transformed into k-space for all k-values allowed by the periodic boundary conditions. The k-dependent matrices are then unitarily transformed, with each unitary matrix being represented by a set of complex rotation matrices. It is shown that the corresponding angles can be interpolated and extrapolated toward the zone boundaries in a straghtforward manner and that this extrapolation can be done from any finite supercell with reasonable accuracy. This gives rise to an infinite system density matrix for which all fundamental properties are guaranteed by construction. This infinite system density matrix may be used to construct a corrected density matrix for the finite supercell calculation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520604
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Extrapolation of real-space quantum chemical calculations from finite-size supercells to the ideal infinite system. III. Application to two-dimensional systems (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 895-911 
    Details
    ISSN: 0020-7608
    Keywords: graphite ; finite supercell ; k-space interpolation ; density matrix ; Brillouin zone mapping ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A previously presented extrapolation method of the density matrix of a standard finite supercell calculation to an infinite supercell is extended to two-dimensional systems. The density matrix of the finite supercell is transformed into q space where it is interpolated and extrapolated in such a way that all its fundamental properties are guaranteed by construction. The resulting modified density matrix contains information from a continuum of q points in the first Brillouin zone which allows for a more realistic calculation of properties like the total energy Etot per atom and the band structure ε1(q). It is shown that this more realistic calculation takes better care of the crystal symmetries and is essential in reproducing both important degeneracies in the band structure and rotationally symmetric results. In the special case of π electrons only, an exact analytical solution for the density matrix of the infinite supercell is presented. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 895-911, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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