 | Acta Crystallographica Section D Acta Crystallographica Section D BIOLOGICAL CRYSTALLOGRAPHY |
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![[Figure 4]](ba5132fig4mag.jpg)
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Figure 4
Crystal twinning through space-group transition from orthorhombic to monoclinic. A macroscopic crystal is shown from the bottom and top view. In the orthorhombic space group, the molecular packing within two volumes in the crystal, labeled A and B, is undistinguishable when viewed from top or bottom, because the orthorhombic crystallographic symmetry relates the content of the two volumes by a twofold (screw) axis. A twinned monoclinic crystal results if the molecules rearrange in the same manner in A as viewed from the top and in B as viewed from the bottom. The monoclinic packing is equivalent in the two volumes but is no longer related by crystallographic symmetry; instead, the twin operator, a 180° rotation around an axis in the plane perpendicular to the unique crystallographic b axis of the monoclinic lattice, relates the diffraction patterns of the two volumes. |
![[Figure 4]](ba5132fig4.jpg)
| BIOLOGICAL CRYSTALLOGRAPHY |
ISSN: 1399-0047
