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. 3.8, p. 342

Section 3.8.10. Quality control

C. J. Gilmore,a G. Barra and W. Donga*

aDepartment of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK
Correspondence e-mail:  chris@chem.gla.ac.uk

3.8.10. Quality control

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Quality control (Gilmore, Barr & Paisley, 2009[link]) is designed for situations where the stability of a material is being monitored over time, for example as part of a production-line system, or for periodic equipment alignment. A set of reference patterns is collected that represents acceptable measurements – any measurement sufficiently close to these references represents a good measurement. Various sample patterns are then imported and compared with those reference patterns, and any that vary significantly from the ideal are noted and highlighted.

The results are best displayed graphically using a variant of the MMDS method, of which an example is shown in Fig. 3.8.17[link]. The reference patterns define a green shaded surface with acceptable sample patterns, coloured red, shown within it, and potentially problematic sample patterns appearing outside it. The volume of the green shape is defined by intersecting spheres around each reference sample and these can be altered to allow more- or less-stringent quality control.

[Figure 3.8.17]

Figure 3.8.17 | top | pdf |

Visualization tools for quality-control procedures using a modified MMDS plot. The red outlier is a sample unacceptably far from the cluster of reference measurements.

References

Gilmore, C. J., Barr, G. & Paisley, W. (2004). High-throughput powder diffraction. I. A new approach to qualitative and quantitative powder diffraction pattern analysis using full pattern profiles. J. Appl. Cryst. 37, 231–242.Google Scholar








































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