I am using Rietveld refinement program (xpert highscore plus with ICDD and ICSD database). I have space group, lattice parameters, atomic positions, occupancy and all refined parameters. Is there any direct formula to calculate the theoretical plot mathematically as well as Bragg reflections(Bragg positions)?
Dear Faisal:
Do you mean the calculation of theoretical XRD pattern from the above mentioned structural parameters? If what I understood is correct, you can do it with programs such as Powder cell or VESTA just by providing with the type of space group and lattice parameters.
I suggest that you can use Fullprof or GSAS softawres for this. I am familiar with full prof. In Fullprof, the first step is to create a pcr file using known lattice parameter values, space group, Wyckoff positions and X-ray wavelength. The procedure to create pcr file is attached.
Once you created the pcr file, then start refining scale, background, lattice parameters, Wyckoff positions etc. Basically you have an experimental pattern, using the known lattice informations (pcr file), the software theoretically produce a pattern (calculated pattern). You keep on refine various parameters, until the theoretical pattern that you have created match well with the experimental pattern. The goodness of fitting is judged from the values of profile parameters such as Rp, Rwp, RB, Chi etc. Ideally chi square need to be reduced to very close to one. RP, Rwp, RB should be much less than 10.
Through Reitveld refinement of XRD data, you may get all the structural details as well as simple things like the hkl values of the Bragg reflections. Reitveld refinement can be performed using number of software's. In this category, Full-Prof is one of most used free software for Crystal lattice magnetic crystal structure refinement.
If you are interested to learn about, how to do Profile fitting of XRD data using Full-prof you can watch below video https://www.youtube.com/watch?v=2SzIfWxYNDs&t=52s
and if your are interested in crystal structure refinement using Full-Prof you can watch below video , it is for beginners and present one of easiest Way to do structural refinement using FullProf Suite https://www.youtube.com/watch?v=mWNpIIwEcDk .
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