Dear Mr Werner,
adding to the remarks by Bob: basically the squared line widths (Gamma^2
in the GSAS manual) must not become negative for any hkl combination. For
h00, 0k0, 00l, negative S400, S040, S004 always will lead to negative
squared widths. If S400, S040 and S004 are all positive, the
Dear Rietvelders
I am doing rietveld on some Zinc Ferrite samples. But when the U V W
parameters are refined the program crashes saying negative Guassian . Please
give your advice in this regard. Also which factors contribute to decrease
in intensity in the refined pattern.
Hysen Thomas
Lecturer
Hi,
Some of the Shkl values for the Stephens' anisotropic broadening can be
negative. However, negative S400, S040 S004 terms have no physical meaning;
best is to probably set them to zero not refine them further. GSAS has a
plotting routine (coupled to gnuplot) that displays the microstrain
