Dear XAFS community,

I start my first EXAFS data analysis practice with Cu first shell fitting.
I have 3 questions:

1.Usually what are the stratages I can use to refine the fitting?The floated parameters for each path will be automatically changed by some modifications,usually what are these modifications?

2.I guess changing the value of fit variables or some experiment data parameters would be 2 stratages for fitting refinement, but the values of them are usually limited in a very short range(cannot be changed much) and when changing the values of them, I am also confused about what kind of changes can generate better fitting, I understand there are maybe no routines for different cases, but are there some trends which can be helpful for getting an improved fitting? I fit the Cu first shell using the first path which is generated by FEFF, the curve of first shell fitting seems ok but the guessed parameter N (initiall guess N=12) is never closed to12 but resulted to be some values around 7, I think there must be some problems, could you give me a help?

3.If there are more than 2 paths that give the same shell the comparable contributions that both cannot be ignored, then how to deal with the resulted different path parameters? For example, if we have to consider 2 major paths for the single shell, then after fitting we get one path parameter Dr1=0.5A, and another path parameter Dr2=0.2A, and the Reff of both paths are different too, then how to identify the final path length(bond length) R for this shell?

Thanks so much.