Hi there,

I am pretty new to Rietveld refinement and I am trying to do the analysis on the std material LaB6 Nist 660a. The goal is to extract the IRF function of the instrument.

I am using Fullprof software to do the refinement.

The best I can achieve is not so good (chi=23, I upload the PCR file). I notice that most of the error is coming from low angle peaks, which are very asymmetric...As you can see in the pcr I already tried to fit the asymmetric coefficient, so I am wondering if is it normal to have this asymmetry with a standard material or should I change some instrumental parameters and redo the measurment? (soller, slits...)

Moreover, should i remove the CuKalpha contribution when doing the refinment of the STD material?

Thank you so much!