that Z is no. of atom in a unit Cell or denoting scale factor or it is something else. I am using GSAS Software which is free available
Please tell me, I am attaching one file I have done the refinement having X2 = 1.91 is that Refinement is acceptable for powder Pattern of alpha, gamma mixed phase Fe2O3 and in PPt base line correction is ok or not and what else Parameter I can change ?
Second is Brookite- anatase (TiO2) Mixture Chi-square is 5.09. I am unable to fit peak near around 36.5 deg. Anatase XRD curve is not matching during fitting Pl. Suggest!! and for Phase fraction calculation also Pl. give valuable information or paper reference
The chi-squared is good in part because the data is not so good, so the agreement between the model and data is okay. You can see from the difference plot that the intensities are not fit particularly well, but it might still be good enough for the quantitative analysis of phase fractions to be fairly accurate. GSAS will output the quantitative result in wt% (if you use the EXPGUI, you can just select the LSTVIEW option to get a text summary of your refinement, including all variables and the wt%).
I really cannot advise you on what more to do, since I don't know what variables you have already refined. It is quite possible that you may have allowed more variables already than are justified by your data. Can you list the variables you have refined for us?
One other point: the data are for Fe-based materials, but you have not said what your source radiation/wavelength was.
Could you tell us the exact phases and measurement conditions? I don't really get it what you were investigating or assuming to see. The data are of quite poor quality. Full pattern refinement enables to extract a lot of information from a powder pattern but then the diffractogram has to have the quality for such an advanced expectation. Otherwise it makes no real sense to apply this technique. From the peak shape I would assume that you have quite small and imperfect crystals.
Jose Sir here it is No. of Atoms in a unit cell
upto what value of deviation Ch--square value is accepted for a pattern because some pattern are not highly crystalline generally powder polycrystalline porous material due to their low calcination temperature than how to refine them properly. Please f someone having any valuable information for this Software please share with me. I am adding one more TiO2 two phase system chi-square is showing 5 for this I dont know what else parameter more I have to change by using this software
I agree. The signal to noise is awful. I would redo the measurement counting for much longer. That pattern is not useful for doing a refinement. I would not trust any of the results no matter what the chi square is since that will be dominated by how well you are fitting the background and noise not the signal.
I agree that the data quality is rather poor, and make things worse you have two low symmetry phases. This data is not good for refinement purpose. As Lawrence pointed, it is better redo the measurement with better statistics.
If I look into the difference plot the signal-noise ration doesn't look that bad, Lawrence, does it? Only the upper presentations using these big crosses makes it terrible looking. What is really insufficient is the refinement: Peak shape is obviously incorrect, and also the peak at 36.5° is badly described what might be texture... But still I do not know the correct phases. It only seems to me that the lightblue phase has perhaps clearly broader peaks which might be the reason also for the reflex anisotropy at 25.
Gert Sir, The phase are Anatase & Brookite of TiO2 but Fitting of Anatase phase is difficult at 36.5 degree and I am getting Bad density value chi-square value is also not coming proper for anatase phase which is very less in quantity. It means this refinement is not acceptable or what I can do pl.Give suggestion!
Mesoporous material do not have high Crystallinity but people have done it in paper I am attaching one paper also from where I am getting pattern like B-2 they have refined similar pattern easily I do not know but they are not given any chi-square value but only Wt% Brookite & anatase they have given
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