Your data is not suitable for relieved fitting, I've corrected some input parameters in the PCR file ( please checkout the attached file)
you can consider the cell parameters somehow, however it is not suitable for scientific research or calibration issue.
to decrease the fluctuations and improve your data signal, so the uncertainty with your fitting would decrease you should :
- first you should increase the X-ray scan time
- the scanning range for 2theta 20 - 90 would be enough for your sample.
- you should increase the scan resolution by decreasing the sampling pitch or the 2theta step( to be 0.01 or smaller)
- you should modify the x-ray machine slits width, try those one: a divergence slit of width DF = 2.4 mm, a scattering slits of width SS = 1.25 mm, and a receiving slit of width RS = 0.9 mm to be used for the data collection.
if you do so I guess your machine output data would be betterز
- your material contains preferred orientation, so try to grind it better and be careful when you prepare the XRD sample, the surface should be smooth somehow and the plate in the XRD machine should be parallel to the surface level 180 degree.
I saw ur .pcr file, it's better to exclude ur data to 30 2theta so u just use 6 or 12 coefficient polynomial, B has negative value, and the preferred orientation present.
I suggest u use GSAS or MAUD, both software has Spherical Harmonic Prefered orientation, or u introduce multiple March Dollase in particular plane.
The data quality is very important. As principle "garbage in garbage out"