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  • 1
    Electronic Resource
    Electronic Resource
    Energetics, electronic structure, and positron annihilation studies of carbon-vacancy complexes in iron (1990)
    Springer
    The European physical journal 81 (1990), S. 281-289 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the density functional theory and the embedded cluster model, we have calculated the energetics of carbon-vacancy complexes in Fe as a function of distance separating the carbon atom(s) and the vacancy along different crystallographic directions. Carbon is found to prefer off-center sites from the vacancy and maintains a constant distance of approximately 3.35a 0 from the nearest Fe atom(s) independent of its direction from the vacancy center. This distance agrees closely with that in stoichiometric Fe3C. Our results suggest that the equilibrium site of carbon is one where it is coordinated to three Fe atoms in its nearest neighbor shell. Further decoration of vacancies by more than one carbon atom has been found to be energetically favorable. The binding of carbon to iron atoms is not caused by charge transfer between the atoms, but rather has a magnetic origin. Positron lifetimes at vacancies and vacancy-carbon complexes have also been calculated for various configurations. Our results are in general agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01309360
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetism and local order (1989)
    Springer
    The European physical journal 12 (1989), S. 361-363 
    Details
    ISSN: 1434-6079
    Keywords: 71.20 ; 36.20.K ; 31.20 ; 73.20 ; 75.20.H
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A simple electronic structure scheme based upon a combination of the molecular clusters and tight binding formulation is proposed that is not only quantitative but also enables electronic structure studies in a computationally efficient manner. As a first application, we use the new scheme to study the magnetic moment of Fe and Ni in a wide range of environments where the local coordination of the magnetic atom changes from two to as many as twelve. This is achieved by considering configurations such as linear chain, crystallographic surfaces of various orientations, thin films and bulk. The magnetic moment is shown to increase with decreasing coordination due to narrowing of electron bands. Its implications for the magnetic moments of small Fe and Ni clusters are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426972
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Impurities and defects in transition metals and their oxides (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 353-366 
    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: Self-consistent local density theory is used to calculate the electronic structure associated with impurities and defects in transition metals and their oxides. An embedded molecular cluster scheme is used in which 15-30 atoms are treated explicitly by the LCAO discrete variational scheme, and the surrounding environment is represented by a potential field. One-electron spectroscopic properties are discussed in terms of densities of states and population analyses; emphasis is placed upon detectable features induced by the presence of defects or impurities. Hyperfine fields and local magnetic moments are examined for binary transition metal alloys, and the effects of local clustering are simulated for comparison with Mössbauer, NMR, and neutron magnetic scattering data. The influence of interstitials and vacancies on metal X-ray absorption near edge spectra (XANES) of the monoxides is evaluated and used to interpret features of the M1-xO K edge spectra. The energy of formation of isolated cation vacancies in Fe1-xO is calculated, and the binding energies of several plausible (m:n) vacancy-interstitial metal defect clusters are presented. We give some semiquantitative explanations for the relative stability of different defect configurations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300733
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical study of the geometry of Mn5 (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 231-236 
    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 geometry of Mn5 in rare gas matrices has been proposed to be a planar pentagon with 25 unpaired electrons. Simple unrestricted Hartree-Fock (UHF) calculations have been carried out using a basis of STO-6G for 1s, 2s, and 2p orbitals with STO-4G for 3s, 3p, 3d, 4s, and 4p in the HONDO5 program. The structure is optimized at the UHF level using the analytic gradient formalism for a planar pentagon. Binding energies and spinmixing are given for the optimized structure.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340827
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    Paper (German National Licenses)
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