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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 83 (1991), S. 267-271 
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The equilibrium lattice parameter and bandstructure of copper monolayers, both in the square (100) and hexagonal (111) symmetry, have been determined using self-consistent full-potential local density approximation (LDA) calculations. Two quite different procedures have been employed: FILMS, a linear-combination-of-gaussian-type-orbitals method, and a full-potential linearized augmented plane-wave (F-LAPW) method. The copper monolayer is bound with respect to the atomic LSDA ground state in the configurationd 10 s 1. Nearest-neighbor distancesa nn are determined as 4.25 a.u. in the square geometry and 4.42 a.u. in hexagonal geometry, the latter being favored in energy by 0.33 eV/atom. Both monolayers thus exhibit a nearest-neighbor distance substantially shorter than that found in bulk copper,a nn=4.8238 a.u. Excellent agreement between the two methods is obtained for the bandstructure, with no indication of ad-band hole at theM point (corner) of the Brillouin zone, in contrast to some other recent self-consistent calculations. Combined use of the von Barth-Hedin LDA and scalar-relativistic corrections produces the smallest gap at theM point, 0.15 eV, at the Hedin-Lundqvist equilibrium geometry. This may be suggestive evidence for the origin ofd-band holes when combined with further approximations in the representation of the one-electron orbitals and the charge density.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 38 (1980), S. 393-411 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: The results of a simple local-density energy band model (Xα) are used to carry through a calculation of the phonon dispersion relations in fcc Ne and Ar. Adiabatic phonons, calculated from the computed Xα total energy surface, are perturbed by the Fröhlich Hamiltonian with electron-phonon matrix elements calculated from the Xα energy bands. The use of low-order perturbation theory gives results in fair comparison with observed values, but shows the general scheme to be feasible. Except for questions of the exact physical content of the Xα model itself, the calculation is entirely ab initio, and is believed to be the first such achieved in insulators.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 1 (1969), S. 109-122 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a one-dimensional linear lattice of particles whose mass, pair potential, and nearest neighbor separation are those of a real rare gas crystal. Numerical solution of the Hartree equation shows that the model behaves as a quantum crystal in the low mass, weak attraction case. In the basic Nosanow cluster approximation the cohesive energy of this helium-like system drops from 6.903°K/N (Hartree) to 3.64°K/N. When all except nearest neighbor correlations in the Jastrow function are taken as unity, the result is 3.69°K/N. For the case of nearest neighbor correlations only, we introduce a positive integral operator with properties akin to those of a transfer matrix and thus form a rigorous upper bound on the cohesive energy of the model system. The convergence rate of the Nosanow expansion is shown to depend on the ratio of the two highest eigenvalues of this operator.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 13 (1973), S. 313-315 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effect of choosing a Jastrow function of the WKB formexp (−k/r5) for use in the Nosanow cluster calculation of the quantum crystal ground state is studied via a previously developed exact one-dimensional model. The computed convergence rates confirm the inability of this form to resum the cluster expansion so as to provide a meaningful variational minimum.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 8 (1972), S. 499-509 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider the convergence and energy-bounding properties of the Nosanow cluster expansion in combination with the pair correlation function employed by Wu and Krumhansl. We employ the transfer-integral method and one-dimensional model quantum solid developed by Trickey and Nuttall. The results of our investigation differ somewhat from those of Wu and Krumhansl. Their correlation function yields a minimum value of the cluster approximation to the cohesive energy for the model system which is significantly different from the rigorous variational result. The cluster approximation gives a substantially different best value of the pair function variation parameter than that determined by the transfer integral. The cluster-expansion convergence rates reflect these difficulties. Restriction of the variation of the single-particle functions to a parametrized Gaussian eliminates these discrepancies. Such nonphysical behavior is a priori possible with any choice of pair function.
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  • 6
    Publication Date: 1991-06-01
    Print ISSN: 0722-3277
    Electronic ISSN: 1431-584X
    Topics: Physics
    Published by Springer
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