Unit Cell Refinement

Nearly all unit cell refinement programs assume that a list of peak positions will be provided in some form. A personal favorite for quick unit cell refinement is the graphical Celref for Windows software of Jean Laugier and Bernard Bochu. Celref also understands space groups and includes a facility to automatically match HKL positions to observed peaks. For use of internal standard, the XLAT software of Bernhard Rupp, despite its age, is very effective. However, 

ABSEN a PC computer program for listing systematic absences and space group determination, P. McArdle, 

International Tables for Crystallography Volume A Space group symmetry, ed. Theo Hahn, Published for the International Union of Crystallography by Springer. Fifth edition, April 2002, ISBN 0 7923 6590 9 ISOTROPY, H. T. Stokes and D. M. Hatch, (2002), http // stokes.byu.edu/isotropy.html 

MAUD (Material Analysis Using Diffraction) a user friendly Java program for Rietveld Texture Analysis and more, 

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Pawley, G.S. Unit-cell refinement from powder diffraction scans. J.Appl. Cryst. 14 357-... 

Figure 1. Results of full pattern fitting (after [53]) of the PXD pattern of an acid-treated phase A sample, based on an orthorhombic unit cell (refined lattice constants a = 7.940(3)A, b = 10.338(4)A, c = 11.591(5)A). The low angle peaks are somewhat asymmetric and are hence not fitted well by the assumed symmetric pseudo-Voigt peak shape.

Pawley, G.S., Unit Cell Refinement from Powder Diffraction Scans, Ibid. 14 357 (1981). 

The sample displacement parameter Ss calculated for each particular case from the displacement (s, in mm) obtained during unit cell refinement as Ss = -36000s/(7tR) or Ss = -144s/7T for the goniometer radius R = 250 mm. 

LAPOD Langford Unit Cell Refinement WWW. ccp 14. ac. uk/ccp/web-mirrors/lapod-langford/... 

XLAT Rupp Unit cell refinement ftp //www-structure.llnl.gov/... 

Full profile fitting can be useful for various tasks including unit cell refinement involving peak overlap, space group assignment, extracting intensities prior to structure solution, and pre-structure refinement fitting of the powder pattern. The two main methods are listed below. 

Table 17.15 Available unit cell refinement software.

Unit cell refinement from powder diffraction data the use of regression diagnostics, T. J. B. 

PAW 81] PAWLEY G.S., Unit cell refinement from powder dif action scans , J. Appl. Cryst, vol. 14, p. 357-361,1981. 

There are problems with the unit cell refinement. 

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