Hi all,
I wonder if the error is due to the sample stage, i.e. error present when capillary is used but not for horizontal sample stage (rotating table)?

-Markus

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 Dr. Markus Valkeapaa
 Department of Chemistry, Helsinki University of Technology
 P.O. Box 6100, FI-02150 TKK

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Peter Y. Zavalij kirjoitti:
Kurt,

It looks like incorrect step size (difference between actual step size and one that is written in the file) or incorrect distance to the detector. The later may incorrect step size if detector is PSD.

I have similar situation with much smaller difference in peak position but the shift (difference between actual and written step size) varies from measurement to measurement. Bruker is working on this but so far no solution/cause is known.

Your case may be simpler if the difference is constant. Perhaps calibration of detector or its distance to the sample is needed.

Best,

Peter Zavalij
X-ray Crystallographic Center
University of Maryland

College Park, MD

Office: (301)405-1861
Lab: (301)405-3230

Fax: (301)314-9121

*From:* Kurt Leinenweber [mailto:ku...@asu.edu]
*Sent:* Thursday, January 08, 2009 6:09 PM
*To:* Rietveld_l@ill.fr
*Subject:* error in peak positions that is linear in theta

Dear Rietvelders,

(I hope this list is appropriate for this question). I am trying to set up a new D8 diffractometer from Bruker, and have it set up with a Vario monochromator focusing on a sample in a capillary. Of course I hope to do Rietveld refinement on the samples eventually. But there is an error in two theta of the peak positions on all samples, and the error is linear in two theta. At 40 degrees the error (measured minus expected) is about 0.020 degrees, at 80 degrees the error is about 0.040 degrees, etcetera.

Has anyone ever seen anything like this and do you know where it could come from?

Thank you very much,

                                                            - Kurt

*********

Kurt Leinenweber

Dept. of Chemistry and Biochemistry

Arizona State University

Tempe, AZ 85287-1604

phone (480)-965-8853

fax (480)-965-2747

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