Figure 4
Non-merohedral twinning in an orthorhombic crystal where 2a = b. (a) The relationship of the unit cells in different domains is a 90° rotation about c. (b), (c) Diffraction patterns from the two different domains in the crystal. The green spots in (b) arise from cells in the orientation shown in green in (a); likewise, the blue spots in (c) come from the blue orientation in (a). (d) Superposition of (b) and (c) to illustrate the diffraction pattern that would be measured for the twinned crystal. Note that blue and green spots only overlap where k is an even number. Both Figs. 3 and 4 were drawn using XPREP (Sheldrick, 2001). |