CCP14
Tutorials and Examples
Automated Crystal Structure Solution from Powder Diffraction Data Using EXPO
Basic run Through of Sirware EXPO
The CCP14 Homepage is at http://www.ccp14.ac.uk
From either an Icon in MS-Windows (or typing expo on UNIX
command line), run expo.
- This brings up the following screen
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- Click on OK and you are then prompted to open up a sir97 control file.
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- Click on the Browse to view what input files are available
and click on the cime.exp file.
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- Click on OK to confirm your selection.
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- Click continue and EXPO will select what it considers to be the best
intervals for the analysis. You can over-ride this if you which. For this
example, we don't wish to over-ride anything, so just press CONTINUE
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- EXPO determines the background. You can zoom and inspect this, but we will
just accept this and CONTINUE.
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- EXPO tries to determine the best peak profile to use, the goes about extracting
intensities in the "regions" it selected - in this case "Region 2".
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- Now it is continuing onto "Region 3".
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- Now EXPO does an extraction cycle on the full pattern.
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- EXPO is now finished the extracting of intensities and now we can
proceed for the direct methods by pressing CONTINUE.
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- EXPO now is Phasing.
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- EXPO is now attempting to place Atoms.
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- EXPO now is assigning elements to the atoms (in this case,
Pink is Nitrogen, Red is Sulphur, Light Blue is Carbon).
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- EXPO now presents a structure to us.
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- As per Sir97, we can rotate the sample around. Those who refer to
schematic structure of cimitidine in Adrich (1996 to 1996)
page 394 (28,541-2) will see the connectivity and atom assignments
seem to closely match eachother.
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- The above statement is more obvious if we change the PLOT STYLE to
include atom labels.
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Rietveld in EXPO
- It is possible to do Rietveld in EXPO and set parameters to be released
as a function of cycle number.
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- as per Sir97, Fourier difference or Obs maps are possible for finding
residual atoms.
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- It is possible (again as per Sir97) to look through the contour maps
at the electron density.
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