Genesis of Rhombohedral Structures and Mode of Polytype Transformations in Close Packing of Identical Atoms

摘要

For the first time, a large number of geometrically possible rhombohedral modifications (polytypes) have been found to exist in close packing of identical atoms (spheres). The stacking sequence ABC : A... is found to be common to all rhombohedral unit cells. The unit cell volumes ofincreasing cell height corresponding to this sequence exhibit an interesting geometric series. Polytypic transformations in both hexagonal close packed (HCP) and rhombohedral close packed (RCP) structures have been studied using the ab-initio process. The results obtained from the sameare interesting and will be extremely useful in explaining the transformations occurring in the real structures of close packed elements and MX compounds.