Of course, surely you can use a second order polynomial function.
in principle you can use any polynomial to describe that. The most common ones for X-rays and CW neutrons are polynomials in tan(theta). The choice of the variable is related to the functional form of the instrumental aberrations. Be warned, however, that a parameterisation is sufficiently good if your machine is well behaving. If (axial) divergence plays a major role, then you need to consider asymmetry in a proper way.
If you do a modelling using the fundamental parameters approach, then you don't need any parameterisation, as the aberration functions already provide for the correct breadth and shape (and their variation with the angle)
Matteo, Cristóbal, thanks to you!
I've applied the function FWHM=U*(tan(th))^2+V*(tan(th))+W. Everything goes well now ;)
.. I hope it is FWHM^2, if you are using that formula (due to Caglioti with ONE t et al.)...
Yes it is the Caglioti, Paelotti and Ricci, Nucl. Instrum. Methods, 35,223 (1958). But that expression can be modified for including addtional effects.
well, Jesus, you made a mistake on the second name! I give up pretending to see it written correctly: Caglioti, Paoletti, Ricci...
Actually, to be precise, the formula as we see it now, is due to Rietveld that used it in his seminal paper on the method (for neutrons though).
Yes you're rigth in the spelling, I will need to correct my glasses for close-reading. Also the second point it's true but the formula is so-called as the CPR., isnít?
Hi every body
its the first time using XRD techniqu . so i would like ask q please?
β_tot=[〖〖(β_hkl)〗^2〗_measured-〖(β_instrumental)〗^2 ]^0.5
how can i find the value β_instrumental.
thanks
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