ISSN:
1432-2021
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Abstract Synthetic almandine garnet, Fe3Al2Si3O12, has been studied by temperature — dependent single crystal X-ray diffraction and57Fe Mössbauer spectroscopy. The Fe2+ doublet in almandine is characterized by a small asymmetry between the high and low-velocity peaks that decreases in magnitude with decreasing temperature from 420 to 15 K. The X-ray results show that the Fe2+ cation is dynamically disordered with an anisotropic motion within the eight-coordinated site in garnet. The magnitudes of the X-ray determined mean-square-vibrational amplitudes of this motion parallel,x ∥, and perpendicular,x ⊥, to the principle axes of the electric field gradient give a calculated angular dependence of the electric quadrupole interaction of theI 1/2 toI 3/2 transitions that agree with the experimentally measured peak ratios. This is the first recognition of anisotropic recoil free fraction of57Fe in silicates.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00198609
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