1. Department of Chemistry, Weizmann Institute of Science, Rehovot, Israel.
2. ^*Permanent address: Edward Davies Chemical Laboratory, University College of Wales, Aberystwyth.

Abstract

To date, the most widely used method of studying line defects in organic solids has been the dislocation-etch-pit technique (see ref. 1 and papers quoted therein). Although this approach has yielded valuable information permitting the identification of lattice imperfections which emerge at habit faces or cleavage planes, it is often necessary, in order to characterize the dislocations more fully, to assume from projection drawings of the crystal structure the planes in which translation gliding is likely to be most feasible. More information about the slip planes arid Burgers vectors may, in principle, be obtained from other techniques which have been extensively applied to metallic and other inorganic solids^2–4; but organic solids present peculiar experimental difficulties. Thus field-ion microscopy⁵ is unsuitable because of the fragility, high vapour pressure and other properties of molecular crystals. Transmission electron microscopy is generally inapplicable because of the marked tendency for organic solids to react under electron bombardment.