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Electron delocalization in ilvaite, a reinterpretation of its 57Fe Mössbauer spectrum

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Abstract

The Mössbauer spectra of ilvaite CaFe 2+2 Fe3+[Si2O7/O/OH] and their temperature dependence between 298 K and 455 K can be satisfactorily least-squares fitted by a superposition of the resonances for Fe2+(8d), Fe3+(8d) and Fe2+(4c). The relative areas under the three resonances are nearly equal and vary only weakly with temperature. No additional resonances or line broadenings have to be introduced, if we assume that the hyperfine interactions of Fe2+(8d) and Fe3+(8d) fluctuate between their values due to electron hopping between the iron ions at the 8d sites. Hopping can be assumed to occur homogeneously among nearly equivalent sites. The fluctuation rate is described by an Arrhenius law with a pre-exponent of about 9 × 108 s−1 and an activation energy of 0.11 eV indicating non-adiabatic hopping. In addition to the intersite hopping process, the strong decrease of the quadrupole splitting and the isomer shift of Fe2+(8d) between 298 K and 360 K suggests the occurrence of intrinsic charge delocalization from Fe2+(8d) which does not involve the neighbouring Fe3+(8d) ions.

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Authors and Affiliations

  1. Physik-Department, TU München, 8046, Garching and KFA Jülich, West Germany

    F. J. Litterst

  2. Institut für Mineralogie, Universität Marburg, 3550, Marburg, West Germany

    G. Amthauer

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  1. F. J. Litterst
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  2. G. Amthauer
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Litterst, F.J., Amthauer, G. Electron delocalization in ilvaite, a reinterpretation of its 57Fe Mössbauer spectrum. Phys Chem Minerals 10, 250–255 (1984). https://doi.org/10.1007/BF00311949

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  • DOI: https://doi.org/10.1007/BF00311949

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