[GSAS-II] Rietveld Refinement without Ins. Param. file

[Toby, Brian H.]

Hi Dylan,

   If you do not have an instrument parameter file (or more exactly a set of parameters that describes your instrument well), you will not be able to get accurate microstrain and size broadening parameters, but that is not always a concern. You can still use the “old fashioned” approach and refine the UVW & XY parameters (perhaps SH/L), but then do not refine the Phase/Data size and strain terms. It can be a bit tricky to get good starting values for the profile, so starting by peak fitting (see tutorial) might be helpful. Another choice is to look for this nice paper:

Kaduk, J. A., and Reid, J. (2011). "Typical values of Rietveld instrument profile coefficients," Powder Diffraction 26, 88-93.

which tabulates parameters seen for a variety of lab instruments, so you can start from something close.

   One last choice is that you can use a fundamental parameters description of your instrument to get a potentially quite accurate set of instrument parameter terms. There is a tutorial on that too.

  Hope this helps.

Brian

On Jul 2, 2020, at 11:22 PM, Dylan J Bardgett via GSAS-II <gsas-ii at aps.anl.gov<mailto:gsas-ii at aps.anl.gov>> wrote:

Hi everyone,

I am doing some Rietveld refinements for a collaborator with some powder XRD patterns, but they do not have any sort of standard to create their instrument parameters calibration. Is there any way to do these Rietveld refinements without jumping through the hoop of calibrating their instrument?

Best,

Dylan
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