TOPAS-Academic TurorialPawley refinement of Y2O3
The data were recorded on the Durham d5000 using variable slits on a sample of Y2O3. The cell parameter is around 10.6 Angstroms and the space group is Ia-3. By clicking through the headings under the "TOPAS_Durham/Lab Pawley Refinement" folder you should be able to create an INP flie and fit the data in TA with an R-factor around 4.5% without changing any of the refinement settings.
Click on the toolbar icon
Open the XInsert folder "TOPAS_Durham / Lab Pawley Refinement" and work down the nodes inserting items as required. The INP file should now look something like the following:
Note that when clicking on the "Cubic" node you need to enter a starting lattice parameter which in this case should be 10.6.
Click on the toolbar icon Alt-Tab to TA. Turn on the viewing of the Chubychev background using the TA menu option View/Curves/Background (or use the toolbar icon); note it is useful to see the fitted background when doing Pawley refinement. Run the refinement; after refinement the TA screen should look like the following:
Note the display of the background and that it looks reasonable.
Alt-Tab back to jEdit and the INP file should look like the following:
Note the red numbers which are the refined parameter values. Also the fitted intensities are inserted by TA after the space_group keyword after refinement. The LIMIT_MIN text is a warning indicating that the associated parameter value is close to its allowed lower limit. This is a good time to view the Technical Reference PDF file and search for LIMIT_MIN. The Technical Reference can be loaded into Adobe Acrobat 6 from within jEdit under the XInsert node of "TOPAS-Academic, INP format/Help" or in TA under the Help menu item. This completes the tutorial.
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[Modified 10-Apr-2021 by John S.O. Evans. Pages checked for Google Chrome.]