In Rietveld refinement process, I got scale value very small which in the range of 10-2 to 10-6 while in few papers and manual of fullprof suggest the value would be in positive integer. When I manually set the value of scale in positive integer and refined this then data not fitted properly. So please guide me the fitting procedure.
Thanks!
Dear Guru Dutt,
In the Rietveld refinement, scale parameter is a fitting parameter, which scales the calculated intensity to the observed intensity. So, this value varies system to system. It may lie in the range which you mention in the question. I think in the manual of Fullprof the value of scale factor should be integer is not mentioned. It should be positive but need not be integer. During refinement people always refine scale factor. So, do not fix the value of scale factor.
Regards
Dinesh Kumar
Full pattern refinement is no cooking course. You need to understand the meaning of all these parameters. Everything what you do not understand don't touch or switch on/off. The mathematics behind is stupid and calculates something as long as you do not have a division by zero or any other forbidden statement (square root of a negative value). In other words, you can simulate whatever you want. The software is only that clever as you are. Like a car. You will not win a race only because you have a racing car. the software only enables you to have a real chance but you need to work hard to win a race. You also will not press any knobs in an airplane during flight since there you know you might kill yourself.
An image or two may help to pin point the problem
The problem generally arises when the Bragg peaks from calculated pattern don't align with observed peaks. This might be due to poor lattice parameters, space group or impure phase..... You need to check these one by one manually...not using fullprof
Scale parameter is typically pretty small. Something like 10^-3 . So the values you wrote here might be the right ones. As Gert mentioned, which negative integer you are talking about?? The scale factor is typically the first parameter to be refined. With this parameter the software tries to match the measured intensities with the calculated ones. It might be that the your sample gave a pretty small intensities and that is why the scale factor you get is pretty small.
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