[GSAS-II] Help with refinement of laboratory xray data

[Nick Weadock]

Hi,

I am attempting to refine diffractograms of the NIST SRM 640c Si standard
that I acquired on an Inel CPS120 diffractometer. I was able to
successfully get out the instrument parameters using peakfit, and the
results are quite good (Rwp ~ 5%).

However, I have no success when I try a refinement on the data.  The phase
data comes from a CIF file, and the calculated reflection positions match
fairly well with the peaks in the data. However, the "refined" pattern does
not follow the data at all (Rwp > 54%) and the background is much larger
than it should be.  I have tried several background functions and have
varied the sample displacement parameters and the lattice parameter, but
nothing helps.

Has anyone experienced a similar situation? Any advice is appreciated.

Thanks,
-- 
Nick Weadock
PhD Candidate, Materials Science
California Institute of Technology
1200 E California Blvd, Pasadena, CA 91125
MC 138-78
x2520
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