Table 3.3.6.4

Hahn, Th.; Klapper, H.

doi:10.1107/97809553602060000644

International
Tables for
Crystallography
Volume D
Physical properties of crystals
Edited by A. Authier

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International Tables for Crystallography (2006). Vol. D. ch. 3.3, p. 405

Table 3.3.6.4

Th. Hahn^a ^* and H. Klapper^b

^a Institut für Kristallographie, Rheinisch–Westfälische Technische Hochschule, D-52056 Aachen, Germany, and ^bMineralogisch-Petrologisches Institut, Universität Bonn, D-53113 Bonn, Germany
Correspondence e-mail: hahn@xtal.rwth-aachen.de

Table 3.3.6.4 | top | pdf |
The four different variants of Japanese twins according to Frondel (1962)

Handedness of twin partners	Azimuthal difference (°)	Twin element = twin law	Label in Fig. 65 of Frondel (1962)
L–L or R–R	0	Irrational twofold twin axis normal to plane $[(11{\bar 2}2)]$	I(R), I(L)
L–L or R–R	180	Rational twofold twin axis $[[11{\bar 1}]\equiv[11{\bar 2}{\bar 3}]]$ ^† parallel to plane $[(11{\bar 2}2)]$	II(R), II(L)
L–R or R–L	0	Rational twin mirror plane $[(11{\bar 2}2)]$	III
L–R or R–L	180	Irrational twin mirror plane normal to direction $[[11{\bar 1}]\equiv[11{\bar 2}{\bar 3}]]$ ^†	IV

^† The line $[[11{\bar 1}]\equiv[11{\bar 2}{\bar 3}]]$ is the edge between the faces $[z(01{\bar 1}1)]$ and $[r(10{\bar 1}1)]$ and is parallel to the composition plane $[(11{\bar 2}2)]$ . It is parallel or normal to the four twin elements. Transformation formulae between the three-index and the four-index direction symbols, UVW and uvtw, are given by Barrett & Massalski (1966

, p. 13).