XAFS measurements in the temperature range 20-473 It at the Fe K-edge of synthetic almandine (Fe3Al2Si3O12) allow us to determine the T-dependence of the XAFS Debye-Waller (DW) factors for each of the two crystallographically independent Fe-O bond distances (Fe(1)-O and Te(2)-O). The XAFS DW factor of the longer Fe(2)-O bond is larger and has a greater T-dependence than the shorter Fe(1)-O bond, which remains constant over the measured T range. The XAFS DW factors are compared with the uncorrelated part of the DW factors derived from a single-crystal X-ray diffraction (XRD) studiy on almandine and are interpreted on the basis of the Einstein model. A comparison with diffraction data shows that the shorter Fe(1)-O bond is significantly affected by correlation in the atomic displacements.
Temperature dependence of disorder and correlation effects in the almandine X-site
ARTIOLI, GILBERTO;
1997
Abstract
XAFS measurements in the temperature range 20-473 It at the Fe K-edge of synthetic almandine (Fe3Al2Si3O12) allow us to determine the T-dependence of the XAFS Debye-Waller (DW) factors for each of the two crystallographically independent Fe-O bond distances (Fe(1)-O and Te(2)-O). The XAFS DW factor of the longer Fe(2)-O bond is larger and has a greater T-dependence than the shorter Fe(1)-O bond, which remains constant over the measured T range. The XAFS DW factors are compared with the uncorrelated part of the DW factors derived from a single-crystal X-ray diffraction (XRD) studiy on almandine and are interpreted on the basis of the Einstein model. A comparison with diffraction data shows that the shorter Fe(1)-O bond is significantly affected by correlation in the atomic displacements.Pubblicazioni consigliate
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