PDFgui fit parameters

[Mohammad Hassan Sultani]

Dear Professors,

Dear colleagues and PDFgui users,

I have some questions about the PDFgui fit parameters, specifically the delta2, the spdiameter, and the constraint temperature factor U_ij.

I am trying to fit multiphase material using PDFgui,
1) What is the relationship between delta2, spdiameter, and U_ij in one phase to another phase in the same fit? What can we say about a parameter such as U_ij or spdiameter if it is larger (x2 to x10) in one phase compared to another phase in the same fit?

2) Are we allowed to consider the same delta2, spdiameter, and U__ij between different phases in a material? Are these parameters pure mathematical parameters or phase-specific parameters? Is the fit valid or not?

I appreciate your answer to my questions.
Best regards

Hassan