It is very frustrating to figure out the exact phase differentiation on the basis of XRD data. There are many reports and each have its own story. Some says monoclinic, and some like rhombohedral or orthorhombic. Can any one please provide the exact clarification of the phase on the basis of XRD.
Greetings
I suggest you perform Rietveld Anlysis (Refinements) by using each phase separately, then compare the results. Good luck.
Thanks for reply. I have already tried for each phase and in each cases there is good fitting but unable to select which one will be the right choice.
All these structures are just small distortions of the basic cubic structure. As a result, most of the diffraction pattern is essentially the same and only low intensity peaks or tiny peak splitting will give a key to tell which one is correct. It is quite possible that these differences will be too small to be visible by standard laboratory equipment, so you might need synchrotron diffraction experiment.
Also, some of the structures might be metastable and depending on the exact synthetic protocol one might get different space groups.
If you have similar Rietveld refinements for different cells often it is good to choose the most symmetrical one with lowest volume of asymmetric unit.
Try to measure your sample overnight with narrow slits and monochromator if possible. For low symmetry cells you will have large peaks overlapping so you need to have very good pattern to see that.
Also, you can use other methods e.g. Raman spectroscopy to get more info about your system.
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