International Tables for Crystallography

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Detecting twinning by merohedry
T. O. Yeates and Y. Tsai. International Tables for Crystallography (2012). Vol. F, ch. 11.7, pp. 311-316  [ doi:10.1107/97809553602060000836 ]

Abstract

The chapter defines various kinds of twinning and focuses on the detection and analysis of twinning by hemihedry. The perfect overlap of lattices causes distinct intensities to be added together, thereby affecting the intensity distribution as well as the apparent symmetry properties of the crystal, to a degree determined by the twin fraction. Equations are presented for identifying the presence of twinning and estimating the twin fraction from an analysis of diffraction intensities. Complicating factors, including anisotropy, pseudo-centring and local noncrystallographic symmetry, are discussed.


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About International Tables for Crystallography

International Tables for Crystallography is the definitive resource and reference work for crystallography. The multi-volume series comprises articles and tables of data relevant to crystallographic research and to applications of crystallographic methods in all sciences concerned with the structure and properties of materials.