X-ray diffraction study of one-dimensional disorder in cadmium iodide crystals

One hundred and eighteen crystals of cadmium iodide have been investigated by X-ray diffraction methods to verify the disorder theory of polytypism in these crystals. The degree of one-dimensional disorder has been evaluated for eighty-two polytypes by intensity measurements on oscillation photographs. The frequency distribution curve of relative abundance of polytypes versus their degree of disorder shows two maxima, one for α₁ ≃ 0.06 and the other for α₂ ≃ 0.26. The results are in agreement with those obtained earlier by Jagodzinski in silicon carbide crystals and provide more information regarding the origin of polytypism in crystals. Fifty-three new polytypes of cadmium iodide, forty-four hexagonal and nine rhombohedral, have also been discovered during the investigation.