Mr. Shushmoy,

When the space group is wrong, then the R-factor has usually very high value, like in your case.

Thank you for your response mam Bojidarka B. Ivanova . I have used matching software(Match) to identify the phase and used the matched card's space group for refinement. How can i know space group from the data i have? (My sample is Strontium Titanate and space group is : pm-3m)

Dear Tarique Hasan Shushmoy ,

The fitting looks ok; it is necessary to check the physical consistency of the result. Visually the Bragg reflections are consistent with the chosen space group and lattice parameters. Check the space group solution's uniqueness, and it may be represented by more than one that satisfies the extinction rules.

Attached is a print from a space group solution for Quartz with several space groups with their specific extinction rules described in the figure. It is visible that for the selected ones, the Bragg reflections are the same for the lattice parameters solution extracted.

However, the counting is so high, and the 100% peak is about 100.000 cps? or counts? Whatever at this high counting rate, any mistaken-correspondence between the experimental and theoretical ones would largely contribute to the chiˆ2. From 30 up to 70, all peaks are shown some residue.

Strontium titanate has known stoichiometry issues due to charge equilibrium and variable oxidation state for Ti and Sr. Have you considered some vacancies? It may be regarded as fitting occupancy.

Stacking fault is another concern. To treat such occurrence, use Pseudo-Voigt axial divergent profile description, which usually improves the fitting.

Best regards,

WNM