SDPD Internet Course

Week 3

Indexing powder patterns, part 2. 


Read deeply chapters 2.3 to 3.1.3, included, of the SDPD tutorial (CD). Another way is to access to the Kunming Workshop (CD) conference text (end of part 2, same chapters). It is always good to have estimated limits, often just for trying to outperform them.

Look again at the SDPDRR-2 indexing step 1 (CD).

Software to download

The most complete integrated package for indexing includes Treor, Dicvol and Ito, and much more. You may download it at :

Crysfire by Robin Shirley (CD: (not public domain, but free for non-commercial use). Read the manual and have a look at the tutorials installed at this CCP14 Web page by Lachlan Cranswick (CD). Then you should be able to solve the exercises below (at least the first), when Crysfire will be running on your PC.
WARNING : Crysfire is free for academic use, so that even if you are working in an industrial Company, you may use it for solving the course exercises. But if you intend to solve some of your Company's problem with Crysfire, you should obtain the lcence for that from Robin Shirley, the program author.

Chekcell, part of the LMGP suite (CD:, is a powder indexing helper tool for unit cell and spacegroup assignment. It can read the Crysfire output (as well as the McMaille .ckm file output). It can help (graphically) either manually or automatically to select through a list of cells, based on a best fit. Have a look at the many CCP14 tutorials on chekcell (CD).


1 - Now is time to see if you are becoming an expert in indexing. No standard mixed with this pattern. Try to calibrate it by the harmonics method, and then index it. It is a synchrotron pattern, (wavelength 1.30041A, synchro.dat). Part of the exercice is that you should convert the ASCII data in the format which you need. In order to show us your new skill in indexing and using the Crysfire software, we ask here for the .smh output file gathering all cell propositions obtained by applying each of the program possibilities inside the package (ITO, TREOR, DICVOL, TAUPIN, LZON,... all of them), but send only the 50 first most probable solutions, we do not want 400 ! However, we suggest that you also use the isolated programs ITO, TREOR and DICVOL with non-default setting, just to see if the Crysfire default settings have not conducted you in a wrong way. Finally propose the unique solution that you think is the correct one.

2 - OK, this is the pattern which was sent to the SDPD mailing list (, and for which we are still waiting for a convincing indexation proposal. Go to the SDPD Mailing List archives and find the discussion and details about it (email N° 113 and next emails). Will you succeed ? Produce also the 50 most probable solutions of the .smh crysfire output.

The next week (or when you will be ready) will be reserved for
extracting structure factors, part 1.
Good luck !