Re: [sdpd] overlapping reflections / preferred orientation

[Leonid Solovyov <l_solovyov...@yahoo.com>]

> On another note a "theoretical question": in the same way 
> one can derive the zero shift on a diffraction pattern by 
> harmonic analysis without an internal standard, is there a 
> way to derive a possible preferred orientation vector 
> without a structural model? and where can I learn more 
> about that?

Actually, this topic was discussed several times in SDPD/Rietveld
lists.
My "duty advice" is:  When the structure model is absent or incomplete,
one can guess the most probable preferred orientation direction from
the shape of (000) Patterson peak. If the preferred orientation is
appreciable enough the
shape of (000) Patterson peak tends to "follow" the crystallite shape.
I use a simple home-made program which outputs the breadths of (000)
Patterson peak in different hkl-directions. From such output I normally
can guess the preferred orientation direction and degree (the
March-Dollase parameter).
Maybe I will include this program into the next release of DDM.

Best regards,
Leonid


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