[2]   AUTOX     (=MRIAAU) V. Zlokasov, J. Appl. Cryst. 25 (1992) 69-72.
[2]   BH        By Hand
[5]   CSD       Package (Akselrud, Grin, Zavalii, Pecharski, Fundamentski)
[42]  DICVOL    (Louër & Louër, Louër & Vargas, Boultif & Louër).
[14]  ED        electron diffraction.
[17]  FZON      (Visser)
[72]  ITO       (Visser)
[1]   LATTPARM  (Visser) (Garvey)
[1]   POWDER
[2]   PROSZKI   (Lasocha & Lewinski)
[1]   TAK       indexing program of Takaki.
[111] TREOR     (Werner)
[1]   UNITCELL  (Visser)(Garvey)
[1]   Stoe package
[1]   YAO

[21]  KNOWN     Already known
[1]   Guessed
[2]   Analogy
 
 

• Calibration by using harmonics.
• Patterns were recorded in the range 5-130 to 150° 2-theta
• 0.02° 2-theta step scan
• Time being 20-40 seconds per point, corresponding to a long week-end
• Sample holder with vertical loading.
• Pattern processing :
• Background estimated and subtracted
• Kalpha-2 eliminated
• In some case the data are smoothed
• Peak positions are hunted by using an algorithm based on derivatives
• The result is a list of angles, d(Å) values and observed intensities.
• 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 the programs
• 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 Bail method.
• 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.