Coloring, Distortions, and Puckering in Selected Intermetallic Structures from the Perspective of Group-Subgroup Relations

摘要

Group-subgroup relations are a compact and concise tool for structure systemization. The present review summarizes the use of B?rnighausen trees for classification of intermetallic structures into structural families. The overview starts with group-subgroup relationships between the structures of the metallic elements (W, In, α-Po, β- Po, Pa, α-Sn, β-Sn) followed by examples for ordered close-packed arrangements that derive from fcc, hcp, and bcc subcells (e.g. CuAu, Cu_3Au, MoNi_4, ZrAl_3, FeAl, MoSi_2). The main focus lies on more complex structures that derive from aristotypes with comparatively high space group symmetry: AlB_2, Fe_2 P, U_3Si_2, BaAl_4, La_3 Al_(11),NaZn_(13), CaCu_5, and Re3B. The symmetry reductions arise from coloring of sites with different atoms or from distortions / puckering due to size restrictions (different radii of atoms). The resulting superstructures are discussed along with the consequences for diffraction experiments, chemical bonding, and physical properties.