Crysfire2020 Version 1.0.9 August 2025
Ron Ghosh, Epsom,

When results of Crysfire2020 have been summarised, these may be compared graphically on Windows systems using the Chekcell program from Jean Laugier and Bernard Bochu. This will display the Crysfire summary file contents. Peak positions from a selected structure can be be compared with the measured set of peak positions and the raw data powder diffraction pattern.

After Chekcell starts it needs to open the raw data powder difraction pattern, the list of measured peaks and the Crysfire summary file..

Use the file menu to access these files:
1. Open your raw powder data file
2. Open the peak position file (option type *.*) project.RFS
3. Open the Crysfire summary file project.SUM

Raw Data Files

This version of Chekcell can only treat a limited number of raw data input formats.

A general powder data conversion utility is PowDLL

Usage - from R. Shirley's original documents

The set of windows will contain cell parameters data and settings, the calculated line positions for the selected cell, and a simplified version of the summary list, in which initially the top solution will be selected. Note that the Figure-of-Merit column ("FOM") will always contain the original merit values read from the summary file. It is at present a limitation of Chekcell that it never recalculates any indexing figures-of-merit, even when it would plainly be helpful to do so.

Simultaneously the calculated line positions will be displayed as a second set of vertical lines below the profile baseline. These are numbered to correspond to the observed pattern and color-coded: blue if they correspond to an indexed line (Chekcell calls this a "checked" line) and green if not observed.

Meanwhile the color-coding of the observed-line will change: indexed lines become blue, while unindexed ones remain black.

There are now many possible routes to proceed. Here is one of them, for further evaluating the list of solutions and trying to select the best solution and, as far as feasible, spacegroup, according to the "principle of parsimony". This means: by selecting the trial cell (and spacegroup) that indexes the most observed lines using the least calculated lines to do so, allowing for systematic absences. This would normally be taken into account automatically in the figure of merit, if it could be recalculated for the revised cell/symmetry hypotheses, but, if you remember, Chekcell can't yet do that. a) Click the Best Solution button. A new window will appear. It is usually best to reduce the minimum number of checked (i.e. indexed) reflections from the maximum possible, so as to see more possibilities, and perhaps some of the other controls, such as excluding triclinic cells if some 90° angles are present). Click on Run to launch the calculation. b) A short list of "best" cells will eventually be presented, using the parsimony principle discussed above. These are often worth investigating further, even if they did not originally give the highest figures of merit.

Another important use of Chekcell is to test for the presence of a higher symmetry lattice than is apparent in the setting reported by the indexing program:
a) Click the Le Page button. A new window will appear. Its Crystal Systems window will initially be showing "All". Since the purpose is to see possible higher-symmetry supercells, click on only those systems that are higher than for the present top solution. Accept the rest of the defaults and press Run.
b) If any geometrical supercells in a higher crystal system are reported, add them to the list by pressing the red Best button. The "best solutions" section at the end of the analysis will hopefully list the possible higher-symmetry spacegroups that this offers.
c) Note which they are, select a suitable one and press Add to add it to the summary list.
d) Click on the Close buttons for "Best" and "Le Page".

Example data for Chekcell

A zip file LiTi_example.zip is available containing LiTi.cpi, LiTi_1.RFS, and LiTi_1.SUM,