Electricfield gradient and meansquareddisplacement tensors in hedenbergite from singlecrystal Mössbauer milliprobe measurements
Abstract
We report Mössbauer milliprobe measurements on small singlecrystals of a magnesiumrich hedenbergite, approximate composition CaFe_{0.54}Mg_{0.46} (SiO_{3})_{2}, in which each of the electricfield gradient and meansquared displacement tensors for Fe^{2+} in the M1 site of the crystal are precisely determined. Each tensor has in common, as required of crystal symmetry, the twofold axis of the monoclinic unit cell, but the principal directions of the two tensors in the perpendicular plane are noncoincident. The meansquared displacements determined in the Mössbauer experiment exceed those determined from the Xray vibration ellipsoids for Fe^{2+}/M1 by a factor of 1.6; the anisotropy in the meansquared displacement tensor from the Mössbauer measurements exceeds that from Xray by a factor of around 5. The ramifications of these differences are discussed.
 Publication:

Physics and Chemistry of Minerals
 Pub Date:
 2000
 DOI:
 10.1007/s002690050003
 Bibcode:
 2000PCM....27..156T