Hello, I was trying to evaluate the phase fraction from a mixture of multiple phases using X-ray diffraction, collected using Cu Kalpha radiation. I went through the GSAS II tutorial video on how to perform Rietveld refinement for multiple phases at https://subversion.xray.aps.anl.gov/pyGSAS/Tutorials/SeqRefine/SequentialTutorial.htm
Started the refinement by setting a constraint which fixes the sum of phase fractions to be one. I am getting a refinement error stating "Invalid metric tensor" when I was trying to refine unit cell parameters and phase fraction together. I will be thankful and appreciate any lead on how to tackle the error. Thank you Angshuman Gupta Indian Institute of Technology Bombay, India [image: image.png]
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