On squaring triangles – Structural motifs in Cu–In–Sb compounds

•Two new ternary compounds Cu7In2.5Sb0.5 and Cu2In0.75Sn0.25.•First ternary Ni2In superstructures with vacancies in the pseudohexagonal network.•Pseudocubic clusters in the pseudohexagonal structures.•Pseudocubic c/a ratios due to the relation to tetrahedrally close packed structures.

Two new ternary Cu–In–Sb compounds Cu7In2.5Sb0.5 and Cu2In0.75Sb0.25 are presented. Both compounds are Ni2In type superstructures with vacancies in the pseudohexagonal network. Additionally, the pseudocubic nature of the compounds and Ni2In type (super)structures, in general, is discussed. Remarkably, a large number of pseudo-five-fold and pseudo-three-fold axes contribute to generate a pseudocubic symmetry in the crystal structure that is reflected in pseudocubic axial ratios in Ni2In type superstructures. We find that they belong to the family of tetrahedrally close packed structures which implies that pseudocubic axial relationships simply are to be expected.

Graphical abstractEvolution of pseudocubic clusters in Sb-doped Cu7In3 and the Cu–In–Sb 2:1 phase.Figure optionsDownload full-size imageDownload as PowerPoint slide