Re: RIET: Refining on R-Bragg rather than R-Wp???

Peter Y. Zavalij ( (no email) )
Thu, 11 Sep 1997 11:31:20 -0400

> Lachlan Cranswick <lachlan@melbpc.org.au> wrote 11 Sept 1997:
>
> >Does anyone know the pros and cons of refining of Weighted R-Bragg
> >instead of the Weighted Profile (R-Wp)?

> Alan Hewat, ILL Grenoble wrote:

> Yeah, that's what people used to do before Hugo Rietveld invented
> profile refinement. But if your resolution is so good that you can
> actually MEASURE all the R-Braggs, why not :-) Otherwise the
> extracted integrated intensities (R-Bragg) are biased by the calculated
> structure factors, since the latter are used to obtain the former.
>
> Alan Hewat, ILL Grenoble, FRANCE <hewat@ill.fr> tel (33) 4.76.20.72.13
> ftp://ftp.ill.fr/pub/dif fax (33) 4.76.48.39.06 http://www.ill.fr/dif/

Moreover, it is much better than using Rietveld refinement, except of course
you have to get integrated intensities for all or most of reflections. In that
case
it works like single crystal data. Unfortunately it works only in case of simple

unit cell with high symmetry.

--Dr. Peter Y. Zavalij    University Crystallographer   Materials Research Center, SUNY at BinghamtonPh/Fax:(607)777-4623  E-mail:zavalij@binghamton.eduhttp://imr.chem.binghamton.edu/zavalij/zavalij.html