[GSAS-II] Refinement error "Invalid Metric Tensor"

[Angshuman Gupta]

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

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