Structure of fault stackings of molecular layers X—M—X in CdI2 polytypic crystals

Abstract

AbstractThe arrangements of molecular layers I—Cd—I, which may be regarded as “faulted” for CdI2 polytypic crystals, are analyzed. Tentative classification of faults into those which are intermediate structure between the basic polytypes 2H and 4H and faults occurring between different blocks of pure structure 4H is proposed. The connection between some growth parameters and the structure of faults in CdI2 crystals grown from solutions is discussed. It is shown that the geometrical classification of stacking faults used for layered inorganic crystals is not appropriate for the description of the faults existing in polytypic crystals of MX2 type. The effect of weak external electric and magnetic fields on the polytypic structure of CdI2 is analyzed. The experiments performed for several hundred of polytypes of CdI2 showed that the external fields may, in some conditions, affect the organization of the polytypic structure of crystals very strongly. In particular, it was found that the external fields may change the period of polytype cells and that the relative number of hexagonal and rhombohedral polytypes differ very strongly for crystals grown in the absence and in the presence of external electric and magnetic fields.