VDF images showing the selected pairs of bend contours at scattering vectors g hkl that are parallel or nearly parallel to the dislocation lines, that is, along the screw component of the Burgers vector, for theophylline form IIIb. The green dashed lines mark the dislocation cores (lines u ), and the red and yellow arrows indicate the scattering vectors g hkl . The grey solid line in d outlines a grain boundary. The white arrows mark the screw components determined using the Cherns and Preston rules 30 . The magenta arrows mark the full Burgers vectors and the blue arrows mark the edge components, determined by geometric self-consistency with each screw component and Burgers vector direction from the g hkl B screw = 0 analysis (Supplementary Fig. 19 ).
