Figure 9
Hexagonal 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 [Sigma]7 twin-related domain II (small crosses, left-handed blue unit cell a2, b2, c2) and of the [Sigma]7 coincidence lattice (large black points, right-handed red unit cell aT, bT, cT). The six alternative twin reflection planes m'(12[\bar 3]0), m'([\overline 3]120), m'(2[\overline 3]10), m'([\overline 5]410), m'(1[\overline 5]40) and m'(41[\overline 5]0) are indicated by dashed lines. The coordinate axes a2, b2, c2 of domain II (blue) are defined by the reflection plane m'(12[\overline 3]0). The right-handed yellow unit cell a3, b3, c3 of domain II is obtained from a1, b1, c1 by a clockwise rotation of [varphi] = 120° + 2 arcsin [(1/2)(3/7)1/2] = 120° + 38.2° = 158.2° around the hexagonal axis (cf. Appendix C[link]). This cell is commonly used in structure determinations.  [article HTML]

© International Union of Crystallography 2012