2.2.2- "Automatic" indexing
 AUTOX (=MRIAAU)
V. Zlokasov, J. Appl. Cryst. 25 (1992) 69-72.
Package (Akselrud, Grin, Zavalii, Pecharski, Fundamentski)
 DICVOL (Louër &
Louër, Louër & Vargas, Boultif & Louër).
 FZON (Visser)
 LATTPARM (Visser) (Garvey)
 PROSZKI (Lasocha &
indexing program of Takaki.
 TREOR (Werner)
 UNITCELL (Visser)(Garvey)
 Stoe package
 KNOWN Already known
Three main programs emerge :
ITO and variants 
and DICVOL .
The strategy applied to the samples
in this scenario was generally :
We will see the results of this general strategy
as applied to the experimental cases retained in this scenario :
Calibration by using harmonics.
Patterns were recorded in the range 5-130 to 150°
0.02° 2-theta step scan
Time being 20-40 seconds per point, corresponding to a
Sample holder with vertical loading.
Pattern processing :
Background estimated and subtracted
In some case the data are smoothed
Peak positions are hunted by using an algorithm based
The result is a list of angles, d(Å) values and
According to the calibration technique retained in this
scenario, harmonics have to be found.
Using a software for cell refinement (as ERACEL for instance)
applied to the fictitious cell corresponding to the harmonics (an orthorhombic
fictitious cell if 3 series of harmonics have been detected), the a, b,
c parameters are refined together with a zeropoint.
The "calibration" is finished.
Now is the indexing stage strictly speaking.... : run
OK, and what to do now if a cell proposition seems convincing
? Check it! The unambiguously indexed reflections have to be selected in
the objective to realize a definitive cell parameters refinement. This
final refinement should be perfect (errors <0.01° 2-theta).
The experts could avoid this unpleasing step, if they
are really sure of themselves, going directly to the next step.
This next step consists in an attempt to extract structure
factors by the Pawley method or the Le
The space group can be estimated at this next step too,
realizing an extraction in a space group without extinction (for instance
choosing P2/m if the system is monoclinic, P4/mmm if it is tetragonal...).
Extracted intensities have to be carefully checked in
order to determine systematic extinctions if any.