An interpretation of three intersections of cubic and rhombohedral structures based on the conservative nature of force skeletons

Abstract

A crystallographic analysis of the structures of inorganic compounds has shown the uniformity of “force skeletons”: pseudotranslational sublattices of atoms determining the structure of different classes of materials. At three specific c hex/a hex ratios, structures with a rhombohedral cell can be considered in the pseudocubic representation with P, I, and F cells (c hex/a hex is, respectively, 1.225, 0.612, and 2.45). The large fraction of structures with c hex/a hex ratios close to these values indicates the stability of these atomic constructions. Force skeletons with a typical hexagonal subcell (different for cations and anions), which reflects the relationship of these structures with the high-symmetry structural types of sphalerite (ZnS) and galena (PbS), have been established for the representative group of sulfides structures with a cell parameter ∼4 A in the direction perpendicular to the mirror plane.