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Rietveld Refinement Negative Peak Value
timedust #1
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Subject: Rietveld Refinement Negative Peak Value
Hello, everyone,

I am using Rietveld refinement to quantify minerals in multiphase samples with TOPAS. I used Jade 9 to determine mineral phases, downloaded cif files from the American Mineralogist Crystal Structure Database, and carried on Rietveld refinement. I got a small Rwp=5.36% at last. However, it was really strange, in the area where several peaks of different phases appeared, the intensity value of some phases would be negative, and at the same time, the intensity of other phases around there would exceed what we measured.

Is there anything I could do to avoid this awkward situation?

Thanks
johnsoevans (Administrator) #2
User title: John Evans
Member since Aug 2009 · 219 posts
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Do you really mean the calculated intensity of the peak is negative, or do you men the intensity is lower then observed?  The only way that calculated peaks can be negative is if you're applying a preferred orientation correction that has refined to extreme values.
timedust #3
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Thank you. After turning off the preferred orientation, the negative peaks disappeared. Though I got a larger Rwp, but the fit showed where the real problem lied. I shall refine the preferred orientation at last.
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