Dear Apu,
if instrumental resolution has been correctly considered, size effects
have been considered, and if the microstrain broadening behaves indeed
such that it can be described with the "Stephens model", definitely the
parameters have a meaning, they quantify the shape and the anisotropy of
the microstrain as a function of the direction of the diffraction vector.
Of course there are different possible origins of the microstrain
distributions. For that you need models, which however, often lead to
something compatible with the Stephens-type anisotropy. What you have to
do is to think about what may be the origin of your microstrain
broadening, and then you have to try to relate the refined SHKL values
with the physical model.
There may be dislocations (look at various papers by T. Ungar),
microstresses (of whatever origin, derived for cubic symmetry 1944 by
Stokes & Wilson; mentioned by Stephens 1999), composition variations
(Leineweber & Mittemeijer 2004; for that case it was explained in
detail, how the SHKL parameters can be used to calculate the width of
the composition distribution) but also other orgins are imaginable.
Definitly the situation is very complicated, if you have several
indepedent microstrain broadening contributions.
Best regards
Andreas Leineweber
[EMAIL PROTECTED] wrote:
Dear All,
I am carying out Rietveld refinement of a deformed polycrystalline sample. WH
plot shows anisotropic broadening of the profile. If I incorporate Stephens
Model in GSAS, it improves the quality of the fit.
Now my question is:
In this case if I use the refined parameters (of Stephens model)to draw the
3D-anisotropic strain field within the sample, does it carry any physical
meaning!
Thanking you.
With best regards,
Apu
--
Dr. Andreas Leineweber
Max-Planck-Institut fuer Metallforschung
Heisenbergstrasse 3
70569 Stuttgart
Germany
Tel. +49 711 689 3365
Fax. +49 711 689 3312
e-mail: [EMAIL PROTECTED]
home page of department:
http://www.mf.mpg.de/de/abteilungen/mittemeijer/english/index_english.htm
