Dynamical transition of myoglobin in a crystal: comparative studies of X-ray crystallography and Mössbauer spectroscopy

2001 ◽  
Vol 30 (5) ◽  
pp. 319-329 ◽  
Author(s):  
S.-H. Chong ◽  
Y. Joti ◽  
A. Kidera ◽  
N. Go ◽  
A. Ostermann ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Comparative Studies ◽  
Mossbauer Spectroscopy ◽  
Dynamical Transition ◽  
X Ray ◽  
X Ray Crystallography ◽  
Mößbauer Spectroscopy

Nature and mechanism of ilmenite alteration: a Mössbauer and X-ray diffraction study of oxidized ilmenite from the Beja-Acebuches Ophiolite Complex (SE Portugal)

2002 ◽  
Vol 66 (3) ◽  
pp. 421-430 ◽  
Author(s):  
J. C. Waerenborgh ◽  
J. Figueiras ◽  
A. Mateus ◽  
M. Gonçalves
Keyword(s):  
Mössbauer Spectroscopy ◽  
Mossbauer Spectroscopy ◽  
X Ray Diffraction ◽  
Ophiolite Complex ◽  
Cation Site ◽  
X Ray ◽  
Mößbauer Spectroscopy ◽  
Ilmenite Structure ◽  
Optical Evidence ◽  
Excess Fe

AbstractIlmenites from the least-altered rocks of the Beja-Acebuches Ophiolite Complex (SE Portugal), with low Ti values and excess Fe, despite rare optical evidence of hematite exsolution, were studied by 57Fe Mössbauer spectroscopy and X-ray diffraction. According to single-crystal XRD the sequence of alternate layers characteristic of the ideal ilmenite structure is preserved, the excess Fe being accommodated in the Ti layers. No superparamagnetic oxides were detected by 57Fe Mössbauer spectroscopy. The typical spectra of bulk αFe2O3 and of Fe3+-containing ilmenite, in the paramagnetic state above 49 K and magnetically ordered at 6 K, are observed. The average degree of oxidation of the ilmenites, estimated from the chemical analysis assuming ideally stoichiometric full cation site occupancies, is also confirmed by 57Fe Mössbauer data. Since our crystal chemistry study gave no evidence of crypto-exsolution textures within the ilmenite with the observed compositions, fast cooling from magmatic temperatures and decomposition of ilmenite in supergene conditions is suggested.

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