Superstructure in the intermetallic compound TmNi2

Abstract The results of neutron and X-ray diffraction experiments at 300 and 4.2 K on the intermetallic compound TmNi 2 indicate that the crystal structure of the two modifications of TmNi 2 observed by us are closely related to the cubic Laves phase structure (C15). From the fit between the experimental and calculated data a consistent set of parameters describing the atomic positions in the F 43 m space group is obtained for one of these modifications, the corresponding lengths of the unit cell being doubled in all three dimensions with respect to the C15 structure. The other observed modification of TmNi 2 has a simple cubic structure, the unit cell being the same size as found for the C15 type.