Structure of amorphous TbNi₂D_2.4 observed by X-ray and neutron diffraction

X-ray and neutron diffraction measurements have been performed to elucidate the structure for amorphous (a-)TbNi₂D_2.4 prepared by deuterium absorption of the C15 Laves phase compound TbNi₂. The results were compared with those for previously reported a-TbFe ₂D_3.0 which shows the concentration fluctuations. Noticeable differences in the arrangements of metal atoms and the occupation sites of D atoms between the two samples were observed in both X-ray and neutron diffraction data. Namely, in distinction from a-TbFe₂D _3.0, the atomic arrangement of a-TbNi₂D_2.4 is relatively homogeneous. Three-dimensional atomic arrangements obtained from the reverse Monte Carlo (RMC) modeling provided us the visual description of the differences in the structures between a-TbNi₂D_2.4 and a-TbFe₂D_3.0. It was found that over 40% of the D atoms occupied 2Ni + 2Tb tetrahedral sites in a-TbNi₂D_2.4.