Davor Balzar wrote :
>I believe that the reason for the former is absence of strain
>and a simple specimen (cubic symmetry, spherical crystallites with isotropic
>broadening) that was chosen. Some people objected to this, but I think that
>was the only possibility to give the round robin a fair chance that results
>won't be wildly different. Besides, more "difficult" sample would disqualify
>most of the Fourier methods of analysis that could not be applied.
If the Round Robin stops on that first sample, it will be a Size Round
Robin, not a Size/Strain Round Robin. I think that, even if some Fourier
methods needing at least 2 well separated harmonics would disqualify,
a more "difficult" sample should be introduced in the Round.
I have one with a small orthorhombic cell, volume ~300 A**3... It is up
to you to receive 300g of that sample, self evolution of a commercial product
(no heating, no human intervention, just aging). "Only" 350 reflections
in the 15-150 3-theta degrees range, wavelenght 1.54056 Angstroms.
But the problem will certainly be : if the reference methods cannot
be applied, then which result will be recognized as the good answer...
In other words, even if Rietveld-derived methods for size-strain
analysis have shown some efficiency in a basic and simple case,
can we consider that they will systematically work with the same
efficiency in a complex case (i.e. a normal case ;-). Remember
that most Size/Strain experts disqualified these Rietveld-derived
methods as giving dubious results, in their opinion.
Best,
Armel Le Bail
SSRR local results at : http://sdpd.univ-lemans.fr/microstruct/ssrr/
