TOPAS-Academic Turorial
Pawley 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 .
Select from the browser the file TA-Tutorials\data\pawley\d5_00450.raw.
After selecting the data file, an input file for running topas with
the same name but extension .inp is created in the same directory.
The jEdit screen should now look something
like the following:
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
to inform TA to work on this file.
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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