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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy of small clusters and very thin transition-metal films : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6328-6330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic anisotropy of 3d-TM clusters is studied in the framework of a d-electron tight-binding Hamiltonian including hopping, Coulomb, and spin-orbit interactions on the same electronic level. Results for the magnetic anisotropy energy and spin-polarized DOS are given as a function of the bond length for the Fe6 cluster. In particular it is shown that the MAE may be qualitatively related to the projections of the orbital moment along the magnetization directions, and that the "in-plane'' anisotropy can be of the same order of magnitude as the "perpendicular'' anisotropy. Using the same Hamiltonian, the problem of the convergence of the magnetic anisotropy energy of very thin films is revisited. By the choice of a basis which mixes spherical harmonics, it is shown that the irregular oscillations of the MAE versus the band filling disappear. For Co(111) excellent stability of the in-plane anisotropy as observed experimentally was found. Finally, the crystal-field effects are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358256
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical study of magnetic impurities in small metallic clusters (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6800-6802 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic impurities in metallic clusters having N≤6 atoms are investigated in the framework of the Anderson model by exact diagonalization methods. Parameters representative of the Kondo limit are considered. The spin gap ΔE=E(S=1,3/2)−E(S=0,1/2) shows a remarkable band-filling dependence that can be interpreted in terms of the cluster-specific conduction-electron spectrum. Finite-temperature properties are calculated exactly in the canonical ensemble. The specific heat Cp(T) and the impurity susceptibility χf(T) present characteristic peaks at temperatures of the order of TK(similar, equals)ΔE/kB [χf(T)∝1/T for T〉TK]. This is interpreted as a finite-size equivalent of the Kondo effect. The structural dependence is illustrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372846
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  • 3
    Electronic Resource
    Electronic Resource
    On the transition from localized to delocalized electronic states in divalent-metal clusters (1991)
    Springer
    The European physical journal 19 (1991), S. 219-221 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transition from van der Waals to covalent bonding, which is expected to occur in divalent-metal clusters with increasing cluster size, is discussed. We propose a model which takes into account, within the same electronic theory, the three main competing contributions, namely the kinetic energy of the electrons, the Coulomb interactions between electrons, and thes ↔p intraatomic transitions responsible for van der Waals like bonding. The model is solved by taking into account electron correlations using a generalized Gutzwiller approximation (slave boson method). The occurrence of electron localization is studied as a function of the interaction parameters and cluster size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448296
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  • 4
    Electronic Resource
    Electronic Resource
    Calculation of the size dependence of the ionization energy and autoionization energy of Hg-clusters (1989)
    Springer
    The European physical journal 12 (1989), S. 365-367 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To study the transition from van der Waals to metallic bonding we calculate the size dependence of the ionization energy and 5d→6p autoionization energy of Hg n -clusters using a parametrized LCAO model. Our results are in good qualitative agreement with experiment. Comparison with experimental results suggests that electron correlations play an important role for the transition from localized (van der Waals-like) to delocalized (covalent or metallic) electronic states occuring in Hg n atn≃13–19.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426973
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  • 5
    Electronic Resource
    Electronic Resource
    Stability of Au 2 2+ : metastability through an excited state? (1991)
    Springer
    The European physical journal 20 (1991), S. 131-132 
    Details
    ISSN: 1434-6079
    Keywords: 31.10+z ; 31.50+w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the stability of doubly charged Auclusters. From a calculation using semi-empirical linear combination of atomic-orbitals (LCAO) method, we conclude that Au 2 2+ in an excited state (3Σ u + or1Σ u + ) is metastable with an energy barrier of about 0.3 eV. In the ground state (1Σ g + ) Au 2 2+ is unstable, except for small values of Δ(=ε s −ε d ) (difference between thes andd atomic energy levels of Au), when a very shallow minimum appears in the binding energy curve. These results are critically discussed and compared with those obtained by different calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543955
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  • 6
    Electronic Resource
    Electronic Resource
    On the stability of Pb n m+ -clusters (1991)
    Springer
    The European physical journal 20 (1991), S. 133-135 
    Details
    ISSN: 1434-6079
    Keywords: 36.40. + d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The stability of multiply charged Pb n m+ -clusters (n ≤ 3;m=0, 1, 2) was studied by solving exactly for the valencep-electrons a many body Hubbard-like Hamiltonian with intra- and interatomic Coulomb interactions. Particularly we obtain that Pb 3 2+ has a metastable ground state, in which Pb 3 2+ has isosceles shape (bond lengthR=3.2 Å, bond angle θ=124°) and a positive binding energyE B =3.4 eV. The activation barrier against dissociation into Pb 2 + + Pb+ is 0.13 eV, yielding a very long lifetime. This is in agreement with recent experiments [1] in which the lifetime of Pb 3 2+ was determined to be at least 10−6 s. Comparison with self consistent Hartree-Fock calculations shows that the metastability of Pb 3 2+ is due to electronic correlations within the paramagnetic ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543956
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  • 7
    Electronic Resource
    Electronic Resource
    Calculation of the electronic properties of metal dimers (1993)
    Springer
    The European physical journal 26 (1993), S. 171-173 
    Details
    ISSN: 1434-6079
    Keywords: 36.40+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The low-energy excitation spectra of metal dimers are determined by solving exactly a realistic many-body Hamiltonian with inter- and intra-atomic Coulomb interactions. Our results for Cu2 and Ag2 are in very good agreement with the excitation energies derived from recent photodetachment experiments. The characteristics of the many-body excited states in these clusters are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425654
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties of 3d-transition-metal alloy clusters: (Fe x Cr1−x ) n (1991)
    Springer
    The European physical journal 19 (1991), S. 263-265 
    Details
    ISSN: 1434-6079
    Keywords: 36.40. + d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present results for the magnetic properties of (Fe x Cr1−x ) n alloy clusters obtained by using a tight-binding Hubbard Hamiltonian in the unrestricted Hartree-Fock approximation. The dependence of the average magnetic moment, local magnetic moments, magnetic order, and cohesive energy on the size and composition of the cluster were determined. In agreement with surface calculations, we find that the average magnetic moment of the alloy is larger than that of the cluster of one element. Forn=15 a transition from ferromagnetic to antiferromagnetic order is obtained forx≈0.4−0.53. We discuss the importance of the overlap interaction in the spin polarized charge distribution of the alloy (e.g., charge transfer, local magnetic moments). The characteristic properties of the mixed clusters are also discussed by comparison with available results for homogeneous clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448307
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  • 9
    Electronic Resource
    Electronic Resource
    Calculation of the electronic properties of neutral and ionized divalent-metal clusters (1993)
    Springer
    The European physical journal 26 (1993), S. 293-295 
    Details
    ISSN: 1434-6079
    Keywords: 36.40+d ; 71.30+h ; 33.80+Eh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic properties of neutral and ionized divalent-metal clusters have been studied using a microscopic theory, which takes into account the interplay between van der Waals (vdW) and covalent bonding in the neutral clusters, and the competition between hole delocalization and polarization energy in the ionized clusters. By calculating the ground-state energies of neutral and ionized Hg n clusters, we determine the size dependence of the bond character and the ionization potentialI p (n). For neutral Hg n clusters we obtain a transition from van der Waals to covalent behaviour at the critical sizen c ∼10–20 atoms. Results forI p (Hg n ) withn≤20 are in good agreement with experiments, and suggest that small Hg n + clusters can be viewed as consisting of a positive trimer core Hg 3 + surrounded byn−3 polarized neutral atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01429173
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  • 10
    Electronic Resource
    Electronic Resource
    Electronic properties of divalent-metal clusters (1991)
    Springer
    The European physical journal 19 (1991), S. 165-167 
    Details
    ISSN: 1434-6079
    Keywords: 36.40. +d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transition from van der Waals to metallic bonding expected to occur in divalent-metal clusters (e.g., Be n , Mg n , Hg n ) as a function of cluster size is discussed. Theoretical results for several electronic properties reflecting this transition in Hg n -clusters are briefly reviewed and compared with available experiments. The limitations of the present theory particularly concerning the role of correlations and van der Waals interactions are discussed and possible improvements are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448282
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