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  • 1
    Digitale Medien
    Digitale Medien
    Antiferromagnetic versus ferromagnetic coupling in Fe/Cr(107) and Cr/Fe(107) : 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. 6989-6991 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have calculated the local magnetic moments and magnetic order for a Fe(Cr) monolayer adsorbed on a stepped Cr(Fe)(107) substrate. The electronic structure at T=0 K has been self-consistently determined within the unrestricted Hartree–Fock approximation of the Hubbard Hamiltonian in the framework of a real-space tight-binding method. In the Cr/Fe(107) system, two magnetic arrangements have been obtained, the more stable being the less frustrated as obtained in the case of V overlayers on vicinal substrates of Fe. An analysis of both solutions in terms of the total energy calculation and the different degree of frustration is presented. For Fe/Cr(107), a two-step periodicity is obtained. The sign of the magnetization at the Fe overlayer changes from step to step. This spin-flop transition is consistent with the two-layer period oscillation recently observed in Fe/Cr/Fe wedge structures, and with the total magnetization determined from in situ magnetometer measurements during growth of ultrathin Fe films on Cr(001).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.358529
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  • 2
    Digitale Medien
    Digitale Medien
    Vanadium: From cluster to semi-infinite crystal : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6207-6209 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Antiferromagnetic coupling between nearest neighbor vanadium atoms is discussed in the case of free-standing cluster and slabs, steps at the surface of V and V islands on Ag(001). In the self-consistent tight-binding derivation of the unrestricted approximation of the Hubbard–Hamiltonian, we have investigated the onset of magnetism in terms of the exchange integral J. For each topological arrangement of the V clusters [free-standing or as overlayer on Ag(001)], various possible magnetic states are considered and transition from nonmagnetic to magnetic order is characterized. The (001) surface is shown to present magnetism for a value of J lower than those for the other crystallographic faces.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352699
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  • 3
    Digitale Medien
    Digitale Medien
    Antiferromagnetic interlayer coupling in Fe/V and Fe/Cr : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4544-4546 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Antiferromagnetic (AF) coupling between Fe and V atoms is observed experimentally at the Fe/V and Fe/Cr interfaces. In the self-consistent tight-binding derivation of the unrestricted approximation of the Hubbard Hamiltonian, we have investigated Fe3Vn (n=1–5) superlattices and Fe3Vn (n=1–5) films. In all cases one finds an AF coupling between Fe and V together with a decreasing oscillation of the induced magnetic moment on the V atoms when the distance from Fe increases. The distributions of local magnetic moments on Fe and Cr layers in Fe3Crn (n=3–5) superlattices have been determined self-consistently. Both AF and ferromagnetic (F) coupling between Fe layers separated by Cr have been studied. In all cases one finds strong AF couplings between Fe and Cr nearest neighbors with an important increase of the Cr magnetic moment at the interface as compared to the Cr bulk value.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348354
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  • 4
    Digitale Medien
    Digitale Medien
    A mass formula for 4He clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7335-7341 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: An analytic expression for the total energy of 4He clusters composed of N atoms is obtained by means of a variational solution of the energy density functional. The energy is calculated as an expansion in decreasing powers of the cluster radius, R∝N1/3. Contributions of volume (R3), surface (R2), curvature (R), constant (R0), (1/R), and (1/R2) are clearly separated in the formula. Chemical potentials, fusion and fission potentials, surface thickness, and unit radii are also obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460217
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  • 5
    Digitale Medien
    Digitale Medien
    Electronegativity of positive ions in the density functional theory (1982)
    Springer
    The European physical journal 305 (1982), S. 31-37 
    Details
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The relation between Mulliken's definition of the electronegativity and the exact electronegativity ϰ=−∂E/∂N, has been studied using the Density Functional Formalism. It has been found than the differences are smaller than 8% and that Mulliken's prescription defines a “relative” scale equivalent to the exact one.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01415075
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  • 6
    Digitale Medien
    Digitale Medien
    Density functional calculation of the electronegativity and other related properties of atoms and ions of the principal groups of the periodic table (1984)
    Springer
    The European physical journal 319 (1984), S. 275-282 
    Details
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The relation between the electronegativityχ of an atom or an ion (χ=−∂E(Z,N)/∂N) and its finite difference (Mulliken like) counterpart has been studied for the elements of the groups IA to VIIA of the Periodic Table, using an approximate Density Functional Theory. Only the valence electrons are taken into account and the effect of the ionic core is simulated by a simple empty core pseudopotential. The first derivative ∂χ/6N of the electronegativity has also been computed. The interest inχ and∂χ/∂N is illustrated by a simple model for the transfer of electronic charge in a molecule. Molecular electronegativities are then computed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01412540
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  • 7
    Digitale Medien
    Digitale Medien
    Electronegativity of fractionally charged atoms in the Density Functional Theory (1983)
    Springer
    The European physical journal 312 (1983), S. 95-98 
    Details
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The electronegativity (identified with the negative of the chemical potential) of atoms and ions has been calculated in several isoelectronic series using the Density Functional Theory. Then, the electronegativities of atoms and ions with fractional nuclear charge have been obtained by interpolation in each isoelectronic series. Similar interpolations have been performed, starting with approximate electronegativities obtained by Mulliken's finite difference approximation. Both sets of results have been compared.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01411664
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  • 8
    Digitale Medien
    Digitale Medien
    Geometrical and chemical environment effects on the magnetism of stepped surfaces of V and V over Fe (1993)
    Springer
    Czechoslovak journal of physics 43 (1993), S. 1045-1050 
    Details
    ISSN: 1572-9486
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract By means of a real-space tight-binding calculation we obtain the spin-polarization of vicinal (1, 0, 2n−1) vanadium surface, and of one V layer deposited on vicinal (1, 0, 2n−1) iron surfaces (n=1,2,3,4). These geometries can be viewed as a staircase on the (001) surface with steps of monoatomic height andn-atoms width. Forn≤2, the pure V stepped surfaces do not show magnetism which is consistent with the absence of spinpolarization at the (101) surface. By contrast, magnetism is always obtained when a V monolayer is deposited on Fe stepped substrate, which is due to the hybridization of d-orbitals of V and Fe. Furthermore, in all the cases where magnetism is obtained, the surface V atoms at the edge of the step result to be antiferromagnetically coupled with all kink atoms. The effect of this local defect on the magnetic structure seems to remain when approaching the (001) surface (n→∞).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01595301
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  • 9
    Digitale Medien
    Digitale Medien
    Density Functional theory of the atomic electronegativity (1981)
    Springer
    The European physical journal 302 (1981), S. 307-310 
    Details
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The atomic electronegativity, identified with the electronic chemical potential of the Energy Density Functional formalism has been studied by using an approximate functional containing gradient corrections. Only the valence electrons are taken into account and the effect of the ionic core is simulated by an empty core pseudopotential. The results are in close agreement with the experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01414261
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  • 10
    Digitale Medien
    Digitale Medien
    Theoretical study of the stability of X N n (n=−1, 0, +1, +2; X=Ag, Cu;N≤25) clusters as a function of size using a non-local density functional formalism (1989)
    Springer
    The European physical journal 12 (1989), S. 209-211 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40 ; 31.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The spherical jellium model and self-consistent Weighted Density Approximation (WDA) to density functional theory have been used to study the stability of X N n (n=−1, 0, +1, +2; X=Ag, Cu;N≤25) clusters. The calculated magic numbers coincide with the observed ones. The first (IP1) and second (IP2) ionization potentials of Ag N and Cu N as a function of size show the typical oscillations induced by the electronic shell-filling effect. IP1 of Cu N is about 0.5 eV higher than IP1 of Ag N in the range studied (N≤25). For both Cu N and Ag N , IP1 appears to converge well towards the respective experimental values of the work function. The use of WDA allows us to obtain bound negative clusters of small size or with a nearly empty external shell, which is not possible using the Local Density Approximation (LDA) [1, 2]. However the electron affinity of X N clusters obtained as the difference of energies of the neutral and the negatively charged clusters, becomes negative forN=2, 3 and 8 (very close to zero forN=8), revealing that WDA needs further refinements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426939
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