Figure 1
Twin intergrowth of `obverse' and `reverse' rhombohedra of rhombohedral FeBO3 (point group [\overline 3]2/m). (a) `Obverse' rhombohedron with four of the 12 alternative twin elements. (b) `Reverse' rhombohedron (twin orientation). (c) Interpenetration of both rhombohedra, as observed in penetration twins of FeBO3. (d) Idealized skeleton of the six components (exploded along [001] for better recognition) of the `obverse' orientation state shown in (a). The components are connected at the edges along the threefold and the twofold eigensymmetry axes. The shaded faces are {10[\overline 1]0} and (0001) coinciding twin reflection and contact planes with the twin components of the `reverse' orientation state. Parts (a) to (c) courtesy of D. Götz et al. (2012BB16); after Hahn & Klapper (2003BB22, p. 406).  [article HTML]

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