2.1- Crystals or not crystals

If you have sufficiently large single crystals in your sample, it would be logical that your structure approach make use of single crystal techniques, not powder. The faster approach for an identification is an automatic cell search on a four-circle diffractometer. Once the crystal sticked, you could obtain the cell in one or a few hours later, depending on your diffractometer characteristics (classic or 2D detector). Of course, the diffractometer should not be yet occupied otherwise you will have to wait for the end of the current campaign of data recording. This could be long.

You can follow the old good way, in fact the normal way, the most advisable one because you will be able to detect twinning, diffusion, superstructures, incomensurability (...) if any : use the photographic techniques (Laue, Weissenberg, Buerger..) unless your single crystal diffractometer is equipped with a 2D detector. If you have patience and choose this way, you can go directly to chapter 2.3 as soon as you will have the cell.

If you don't have crystals or if you have no patience and you consider that it could be easier/faster to try an automatic indexing by using powder diffraction data, then read the next part. Remember of electronic microdiffraction as a possibility, not as easy as you could think, and don't forget to confirm the result by refining the cell parameters according to the powder diffraction pattern.


Copyright © 1997- Armel Le Bail