>anisotropic size broadening, if included at all, is still mainly
>accomplished through Greaves platelets model (cos(phi) correction). This
>would work satisfactory in this case, but not for a more complicated
>anisotropic size broadening.
You are too pessimistic here. The Greaves model was first used in 1985.
At the same time, anisotropic size modelled by an ellipsoidal mean
crystallite was applied in a Rietveld program. But it is true that most
Rietveld programs are proposing a phenomenological approach :
they fit (spherical harmonics) nicely anisotropic effects, including
effects due to stacking faults, but they do not propose any direction-
related mean size value (or am I pessimistic too ?-). The manuscript
and the next Round Robin steps could benefit from an open discussion
here, and viewpoint exchanges. This is not time lost (I hope).
Have a nice week-end,
Armel Le Bail
Université du Maine
Laboratoire des Fluorures,
Av. O. Messiaen,
72085 Le Mans Cedex 9
