Tilt boundaries in single crystals of cadmium iodide. II. Formation of closed rings on X-ray photographs

The X-ray a-axis Laue photographs of single crystals of cadmium iodide grown from solution sometimes show closed rings of various shapes, viz. hexagonal, trigonal, etc. and of various sizes, corresponding to each X-ray reflection. They have been satisfactory explained in terms of the formation of more than two tilt boundaries of dislocations during crystal growth. The boundaries result from a vertical alignment of triple nodes of dislocations created by simultaneous slip along close-packed directions. In most cases the slip is confined to the basal planes and occurs at regular intervals.