Didysprosium hepta­nickel

The title compound, Dy₂Ni₇, adopts the β-Gd₂Co₇-type structure type. The asymmetric unit contains two Dy sites (both site symmetry 3m) and five Ni sites (site symmetries .m, .2/m and -3m, and two 3m). The four different Ni coordination polyhedra are Frank–Kasper icosa­hedra formed by five Dy and seven Ni atoms, four Dy and eight Ni, three Dy and nine Ni, and six Dy and six Ni atoms, respectively. The two different Dy coordination polyhedra are either pseudo Frank–Kasper icosa­hedra formed by two Dy and 18 Ni atoms or normal Frank–Kasper icosa­hedra formed by four Dy and 12 Ni atoms.

Redetermination of dysprosium trinickel from single-crystal X-ray data

The crystal structure of the title compound, DyNi₃, was redetermined from single-crystal X-ray diffraction data. In comparison with previous studies based on powder X-ray diffraction data [Lemaire & Paccard (1969). Bull. Soc. Fr. Minéral. Cristallogr. 92, 9-16; Tsai et al. (1974). J. Appl. Phys. 45, 3582-3586], the present redetermination revealed refined coordinates and anisotropic displacement parameters for all atoms. The crystal structure of DyNi₃ adopts the PuNi₃ structure type and can be derived from the CaCu₅ structure type as an inter­growth structure. The asymmetric unit contains two Dy sites (site symmetries 3m and -3) and three Ni sites (m, 3m and -3m). The two different coordination polyhedra of Dy are a Frank-Kasper polyhedron formed by four Dy and 12 Ni atoms and a pseudo-Frank-Kasper polyhedron formed by two Dy and 18 Ni atoms. The three different coordination polyhedra of Ni are Frank-Kasper icosa­hedra formed by five Dy and seven Ni atoms, three Dy and nine Ni atoms, and six Dy and six Ni atoms.