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Figure 4
Tetragonal lattices (a–b planes, common c axis pointing upwards) of twin domain I (start domain, lattice points small circles, right-handed green unit cell a1, b1, c1), of the Σ5 twin-related domain II (small crosses, left-handed blue unit cell a2, b2, c2) and the Σ5 coincidence lattice (large black points, right-handed red unit cell aT, bT, cT). The four alternative twin reflection planes m′(120), m′(2[\overline 1]0), m′(310) and m′([\overline 1]30) are indicated by dashed lines. The coordinate axes a2, b2, c2 of domain II (blue) are defined by the reflection plane m′(120). The right-handed yellow unit cell a3, b3, c3 of domain II is obtained from a1, b1, c1 by a clockwise rotation of φ = 2 arctan  (1/2) = 53.13° around the tetragonal c axis (cf. Appendix C[link]). This cell is commonly used in structure determinations.

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ISSN: 2053-2733
Volume 68| Part 1| November 2012| Pages 82-109
doi:10.1107/S0108767311032454
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