At 15:04 28.04.99 +0200, you wrote:
>We would like to use the variable slit attached with our diffractometer for
>Rietveld refinement. I have read the basic papers on the subject : Modern
>Powder Diffraction + the paper by M.E.Bowden et al � Comparison of
>intensities from fixed and variable divergence X-ray diffraction experiments
>� in Powder Diffraction, Vol 6, No. 2, June 1991 + the few lines in the
>Lebail site � low FWHM and Rp� found at
>http://pcb4122.univ-lemans.fr/powdif/low_fwhm_and_rp.html.
>
>my questions are :
>
>is there a large discrepancy to the theoretical expression :
>IFDS/IVDS=1/sin(theta) ?
>then could we simply applied this correction on the data, and then performed
>a regular Rietveld refinement with Fullprof or GSAS ?
>Is there any comparison beetwen structural data obtained by the both FDS
>(Fixed Divergence Slit) and VDS (Variable Divergence Slit) ?
>
Hi Francois,
there is a paper
Peplinski B., Wenzel J.
Proficiency Testing of Instruments - a Key Element for Quality Assurance in
X-ray Powder Diffraction Part 1: ..
Abstract in Proc. EPDIC-6 p. 379 (Poster 12-13). The full paper will be
published in Mat. Sc. For. and was sent to the participants of the round
robin "ratio of the contents of the alpha- and beta-Si3N4 phases by X-ray
or neutron powder diffraction using the Rietveld method" organized by BAM
Berlin.
[EMAIL PROTECTED]
This paper describes errors in variable slit intensities and the methods
for their detection.
We checked (not so extensive) the BGMN intensity handling on the known
Round Robin sample PbSO4 as described in
J. Appl. Cryst. 25 (1992) pp. 589-610.
See:
http://www.bgmn.de/vardiv.html
We got no obvious systematic errors if the divergence does not exceed a
certain level, in comparison to the take-off angle. But we agree with
Burhard Peplinski and Lachlan (cited on Armel LeBails site): There is a
need for testing the alignement and coupling formula of the ADS.
Reinhard Kleeberg
