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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 97 (1995), S. 35-47 
    ISSN: 1434-6036
    Keywords: 71.10.+x ; 71.20.Ad ; 78.20.-e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structures of the cubic layeredd 1 metals LaI2 and CeI2 were calculated using local density-functional theory and the linear muffin-tin orbital method. Special care was taken in the sphere packing used for the atomic spheres approximation. the band structure and the bonding were analysed in terms of projections of the bands onto orthogonal orbitals. The conduction-band structure could be calculated with a down-folded two-orbital basis which then served for the construction of an analytical 2×2 orthogonal, two-center tight-binding Hamiltonian. The conduction band has almost pure Ln-Ln 5d e g character. Thex 2−y 2contribution dominates and is two-dimensional and short ranged. Strong hybridization with the 3z 2−1 orbital occurs near the saddle point, which is thereby lowered in energy and bifurcated due to thek z -dispersion provided by the 3z 2−1 orbital. This strengthens the metal-metal bonds and prevents the nesting instability of the Fermi surface of the half filledx 2−y 2band. Within the limited accuracy of the LDA, the band structure of CeI2 was found to be identical to that of LaI2. The conduction-band 4f hybridizationV d f 2 (0) was analysed and found to be several times smaller than in fcc γ-Ce, in qualitative agreement with recent photoemission results [1]. Of importance for this reduction seems to be that the conduction band is formed by essentially only one orbital, $$Ce 5d_{x^2 - y^2 } $$ ,that the number of Ce nearest-neighbors is small, and that the Ce−Ce distance is relatively large.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7357
    Keywords: 74.72. Jt ; 74.25. Kc ; 63.20.Kr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The equilibrium structure, energy bands, phonon dispersions, and s- and d-channel electron-phonon interactions (EPIs) are calculated for the infinite-layer superconductor CaCuO2 doped with 0.12 holes per CuO2. The LDA and the linear-response full-potential LMTO method were used. In the equilibrium structure, oxygen is found to buckle slightly out of the plane and, as a result, the characters of the energy bands near εF are found to be similar to those of other optimally doped HTSCs. For the EPI we find λs ~ 0.4, in accord with previous LDA calculations for YBa2 Cu3O7. This supports the common belief that the EPI mechanism alone is insufficient to explain HTSC. $$\lambda _{x^{^2 } - y^2 }$$ is found to be positive and nearly as large as λs. This is surprising and indicates that the EPI could enhance some other d-wave pairing mechanism. Like in YBa2 Cu3 O7 the buckling modes contribute significantly to the EPI, although these contributions are proportional to the static buckling and would vanish for flat planes. These numerical results can be understood from a generic tight-binding model originally derived from the LDA bands of YBa2 Cu3O7. In the future, the role of anharmonicity of the buckling-modes and the influence of the spin-fluctuations should be investigated.
    Type of Medium: Electronic Resource
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