[GSAS-II] Calibration of histograms to known peaks

[Gallington, Leighanne C.]

Do you still have access to your sample mount?  The most straightforward way would be to measure how much the sample was shifted up or downstream with a ruler as a starting point and see how much that improves things.
For the custom calibration approach: You can add custom calibrants to the drop down menu by creating a UserCalibrants.py file.  There are instructions in the ImageCalibrants.py file in the GSAS-II folder for the exact formatting.  This approach won't work if the copper peaks aren't sharp enough.
Another approach would be to calculate the shift in expected vs measured position for each copper peak, then interpolate a smoothly varying function and apply that correction to your data. This will only work for peaks inside the range of the copper peaks--the position of any peak at lower 2theta than the first Cu peak will be unreliable.

--
Leighanne C. Gallington, Ph.D.
Assistant Chemist
Advanced Photon Source (X-ray Science Division)
Argonne National Laboratory
Argonne, IL  60439
gallington at anl.gov

________________________________
From: GSAS-II <gsas-ii-bounces at aps.anl.gov> on behalf of Agyeman-Budu, David Nana via GSAS-II <gsas-ii at aps.anl.gov>
Sent: Friday, May 21, 2021 3:17 PM
To: gsas-ii at aps.anl.gov <gsas-ii at aps.anl.gov>
Subject: [GSAS-II] Calibration of histograms to known peaks

Hello all,

I am looking for assistance to calibrate my operando XRD images without using the default calibrants, but with Cu peaks in my data. I found out that the peaks in the my operando XRD data are shifted, and this is due to the sample-to-detector distance differences between my LaB6 calibration measurement and the operando measurement (the sample cell mount increased the distance away from the detector). Even though I have a good calibration I cannot apply it correctly to reduce my data. It also seems that choice of calibrants in the calibration controls are limited to what is available in the drop box.

Any advice or help on this would be appreciated.

Thanks,
David

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