Mössbauer investigations and molecular orbital calculations on epidote

The electronic structure of iron-rich epidote has been investigated by cluster molecular orbital calculations in local spin density approximation. Calculated quadrupole splittings for Fe(III) at both the M1 and M3 sites are in quantitative agreement with the experimental values obtained by Mössbauer...

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Bibliographic Details
Published inPhysics and chemistry of minerals Vol. 28; no. 9; pp. 675 - 681
Main Authors Grodzicki, M., Heuss-Assbichler, S., Amthauer, G.
Format Journal Article
LanguageEnglish
Published Heidelberg Springer Nature B.V 01.10.2001
Subjects
Anisotropy
Clusters
Compressive strength
Coordination
Electric fields
Electronic structure
Iron
Mathematical analysis
Molecular orbitals
Mossbauer spectroscopy
Quadrupoles
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Summary:The electronic structure of iron-rich epidote has been investigated by cluster molecular orbital calculations in local spin density approximation. Calculated quadrupole splittings for Fe(III) at both the M1 and M3 sites are in quantitative agreement with the experimental values obtained by Mössbauer spectroscopy. A detailed analysis of the theoretical results shows that a strong tetragonal compression of the M3 octahedron is responsible for the unusually large value of the quadrupole splitting of FeM3(III). The corresponding electric field gradient (efg) is dominated by the anisotropy of the valence shell of iron, whereas the ligands contribute only about 15% to the efg. The calculations emphasize that rather large clusters, extending beyond the second coordination sphere of iron, are necessary for a reliable description. Small clusters including only the first coordination sphere of iron generally yield misleading results due to unsaturated oxygen bonds and relatively large cluster charges.
ISSN:0342-1791
1432-2021
DOI:10.1007/s002690100150