During the growth of cadmium iodide crystals from solution, it has been observed that
sometimes the crystal suddenly rotates. Probably, the convection currents are providing the force for
the rotation. Mathematically, this force can be estimated and it must be greater than the van-der Walls
force acting between adjacent sandwiches of cadmium iodide and can give rise to polytypic phase
transformations. Further, studies of vacancies and the density measurements of variou s polytypes can
help in understanding the phenomenon of polytypism better