The "Indexation" pulldown menu:

"Options":

Select this button to modify the options used during the indexation of an experimental diagram. The corresponding menu looks as:

  • The indexation procedure consists in comparing the angle between the two first experimental spots, previously given in the "Data" menu, with all the angles between the nodes in the reciprocal lattice inside a certain zone. It explains why it is important to choose spots with low Miller indexes in the "Spots" sub-menu, to explore a small zone, thus decreasing the computation time.
    By default laueX explores all the (h,k,l) space between -3 and 3. You may increase these limits up to 4, but larger values are not reasonable.

  • This menu also allows to fix the angular tolerance used during the angle comparison. The default value is 2 degres and seems reasonable.

    "Try indexing":

  • Selecting this button runs the indexation procedure. It may needs some time according to the speed of your computer: please wait !

  • If the program does not find any solution, you may:
    - increase the zone of the reciprocal space to be explored (but not too much: see previous paragraph).
    - increase the angular tolerance.
    - verify your data: distance from crystal to the detector and coordinates of experimental spots.

  • If there are many possible solutions, the program keeps only the first ten. If these solutions does not match the experimental diagram, you may add some additional experimental spot or decrease the angular tolerance.

    "Solutions":

    When the indexation is done, the choice of one of the possible solutions is made by selecting this button. A menu shows one solution per line, as for instance:

    The indexes found for each experimental spot are displayed. To select one of the solutions for simulate, just click on the corresponding line. In the example shown above, one shall first try solution 2 because it is the one giving the lower Miller indexes for the spots.

    By comparing the experimental diagram to the simulated one for each possible solution, you will find the orientation of the crystal.