Mechanism of production and growth inhibition of collision crystallites

Abstract

When crystals collide in a supersaturated solution there are often produced large numbers of crystallites in the size range below 10 µm: moreover most of these grow extremely slowly. It is now suggested that the formation of these bodies is directly related to the Darwin mosaic structure, which may be modified by the plastic deformation which precedes brittle fracture. This should result in a collision crystallite containing far fewer dislocations or mismatch boundaries than the parent crystal, with consequent much slower growth rate. Alternatively there are independent grounds for expecting all very small crystals to be free from dislocations. There appears to be a general connection between smallness and non-growth, since platelet crystals and whiskers also have thicknesses of < 10 µm in the directions in which they do not grow.