Electron-phonon coupling in mixed-valence systems
Miguel Kiwi1991, Physical Review B
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Abstract
The electron-phonon interaction in mixed-valence systems is modeled on the basis of an Anderson-like Hamiltonian that describes a cluster of one metallic rare-earth cation surrounded by six anions. Coupling between the electronic and phononic variables is introduced, keeping two diR'erent phonon modes: a breathing and an asymmetric mode. The erst, related to the ionic radius, is treated exactly. The asymmetric mode, which determines the sd fhyb-ridization, is dealt with in the Born-Oppenheimer approximation. A variety of experimental results are adequately accounted for by this simple model, like the anomalous thermal expansion, the Debye-Wailer factor, the phonon softening and broadening, and the charge-distance correlation,
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