The "Indexation" pulldown menu:
Select this button to modify the options
used during the indexation of an
experimental diagram. The corresponding menu looks
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.
Selecting this button runs the indexation
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
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.