At 16:08 27.09.99 +0200, Luca Lutterotti wrote:
>If the anisotropic broadening is due to crystallite and/or microstrain
>and/or planar faulting there are Rietveld programs that allows anisotropic
>broadening. The first work on that was again due to Armel Le Bail (anything
>seem to go around him) (French congress, I didn't have the reference on my
>desk now), but actually there are more options availables.
>Maud is one of these Rietveld program (use the Popa model for anisotropic
>broadening and also planar defect from Warren models). I should remark the
>goodness of the Popa model (J. Appl. Cryst. (1998). 31, 176-180).
>But probably you should got a reply also from Bergmann that bgmn will do
>anything.
>
About the BGMN features dealing with anisotropic peak broadening:
BGMN will not do anything, but the following:
1. crystallite shape caused broadening by a maximal six parameter function,
corresponding to the crystal system (B1=ANISO, predefined function)
2. microstrain caused broadening by a tensor of 4th stage (in the same way
as P.W. Stephens oral presentation on EPDIC-5, Parma) (k2=ANISO4,
predefined function)
3. formulations of disorder caused broadening by means of the formula
interpreter (e.g. selective broadening models for special classes of hkl)
4. all of this also for so called subphases, e.g. for modelling of bimodal
crystallite size distributions or of different crystallite shapes for the
same structure.
Reinhard Kleeberg
