Structure and growth of a new polytype of cadmium iodide 22H

Abstract

A 22-layered new polytype of cadmium iodide, designated as 22 H c , with unit cell dimensions a = 4.24 Å, c = 75.18 Å has been discovered. The detailed structure of the polytype has been worked out. It is shown that this polytype is based on a 2 H ideal structure. The polytype 22 H c is so far the largest of the cadmium iodide polytypes whose detailed structure is known. The growth of the polytype has been discussed in terms of screw-dislocation theory and the difficulties which arise in this are pointed out.