to comment on your note below. I also find that you cannot separate these
parameters. I have a deep suspicion that the reason lies elsewhere in the
alignment of the diffractometer. Perhaps the divergence slit not centered
on the beam, the axis of the diffractometer not quite parallel to the
source, the receiving slit not parallel, etc. The problem seems to be
related, as you say, to poorer than expected resolution and greater than
expected asymmetry.
I would think the elements of design are sufficiently well known that the
expected resolution/asymmetry could be calculated for a set of parameters
(source dimensions, take-off angle, divergence slit width, soller
dimensions) but I don't know how to do this or what the bench marks would be.
regards,
Tony Raftery
Technologist
Xray Analysis Facility
Queensland University of Technology
Brisbane, Australia.
At 10:46 AM 3/25/98 +0000, you wrote:
>
>Dear Peter
>
>I fully agree with you that sample height is the one parameter to refine
>and that and that this parameter has a rather different angular
>dependence. However, in agreement with Rory experience we are never able
>to refine sample height in Bragg-Brentano geometry on the Siemens D5000
>with alpha1. We found that the correlation between those parameters was
>always close to 100%. And yes this is with data collected up to 120 deg 2
>theta. By the way how do you model your asymmetric peak shapes? I allways
>find that this parameter in the peak profile correlates highly with all
>the parameters mentioned earlier, including the lattice parameters.
>
>
>Jaap Vente
Tony Raftery
Senior Technologist
Xray Analysis Facility
AEM & XAF
Faculty of Science, GP
Queensland University of Technology
Brisbane AUSTRALIA
ph +61 7 3864 2271
fax +61 7 3864 5100
email a.raftery@qut.edu.au