International
Tables for
Crystallography
Volume H
Powder diffraction
Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk

International Tables for Crystallography (2018). Vol. H, ch. 3.5, p. 282

Section 3.5.1. Introduction

A. Le Baila*

aUniversité du Maine, Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France
Correspondence e-mail: lebail@univ-lemans.fr

3.5.1. Introduction

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Collecting the structure-factor amplitudes |Fhkl| is the key step leading to structure solution from powder-diffraction data, just as from single-crystal data. However, there are specific difficulties and pitfalls associated with powder data, mainly because of diffraction-peak overlap. Once indexing is realized, data reduction to |Fhkl| is a fast process, using whole-powder-pattern decomposition (WPPD) methods. This comfortable situation was not attained without past efforts, which are reviewed in this chapter. The introduction of modern WPPD methods occurred slowly and progressively over the past 30 years, thanks to increases in computer power, improvements in graphical user interfaces, diffractometer data digitalization, the availability of synchrotron and neutron radiation, and last but not least, the proposition of new algorithms. Innovations were not instantly accepted, this also being true for the Rietveld (1969[link]) method, or could not be applied immediately to every type of powder data. Predecessors of the current WPPD methods extracted peak intensities without restraining the cell, so that each peak position was a parameter to be refined (as well as the peak intensity, and the peak shape and width). This is still useful if the aim is to obtain peak positions for indexing, although simple derivative methods can make searching for peak positions faster. Taking advantage of the indexing (Bergmann et al., 2004[link]), new WPPD methods that applied cell restraints to the peak positions opened the door to a long list of new possibilities and applications (including first indexing confirmation and manual or automatic space-group estimation) which are detailed in this chapter. A partial review of the applications realized in thousands of published papers is given, and the evolution of the methods will be discussed. Additional information on the topic of reduction to |Fhkl| values can be found in the books by Young (1993[link]), Giacovazzo (1998[link]), David et al. (2002[link]), Pecharsky & Zavalij (2003[link]), Clearfield et al. (2008[link]) and Dinnebier & Billinge (2008[link]) or in selected reviews (Toraya, 1994[link]; Langford & Louër, 1996[link]; Le Bail, 2005[link]).

References

Bergmann, J., Le Bail, A., Shirley, R. & Zlokazov, V. (2004). Renewed interest in powder diffraction data indexing. Z. Kristallogr. 219, 783–790.Google Scholar
Clearfield, C., Reibenspies, J. & Bhuvanesh, N. (2008). Principles and applications of powder diffraction, pp. 261–309. Oxford: Wiley.Google Scholar
David, W. I. F., Shankland, K., McCusker, L. B. & Baerlocher, Ch. (2002). Structure Determination from Powder Diffraction Data, IUCr Monographs on Crystallography, Vol 13. New York: Oxford University Press.Google Scholar
Dinnebier, R. E. & Billinge, S. J. L. (2008). Powder diffraction: theory and practice, pp. 134–165. Cambridge: RSC Publishing.Google Scholar
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Le Bail, A. (2005). Whole powder pattern decomposition methods and applications: A retrospection. Powder Diffr. 20, 316–326.Google Scholar
Pecharsky, V. K. & Zavalij, P. Y. (2003). Fundamentals of powder diffraction and structural characterization of materials. New York: Springer.Google Scholar
Rietveld, H. M. (1969). A profile refinement method for nuclear and magnetic structures. J. Appl. Cryst. 2, 65–71.Google Scholar
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