X-Ray and neutron diffraction studies of atomic scale structures of crystalline and amorphous TbFe₂D_x

Both X-ray and neutron diffraction techniques were employed in order to elucidate short-range structures of crystalline (c-)TbFe₂D_3.8 and amorphous (a-)TbFe₂D_x (x = 3.0, 2.0) prepared by deuterium absorption of the C15 Laves phase compound TbFe₂. Interatomic distances and coordination numbers were derived from the radial distribution functions, RDF(r)s. The RDF(r)s observed by X-ray diffraction indicated that c-TbFe₂D_3.8 adopts a rhombohedral structure, but there is a little difference in the arrangement of metal atoms between the original C15 Laves phase c-TbFe₂ and the rhombohedral c-TbFe₂D_3.8. In contrast, our results indicated that there is a large difference in the arrangement of metal atoms between c-TbFe₂ and a-TbFe₂D_x (x = 3.0, 2.0) and there are clusters of Fe and Tb atoms in a-TbFe₂D_x (x = 3.0, 2.0). RDF(r)s observed by the neutron diffraction indicated that the D atoms occupy tetrahedral sites consisting of 2Tb + 2Fe in c-TbFe₂D_3.8, while they occupy sites consisting of 4Tb, 3Tb + 1Fe and 2Tb + 2Fe in a-TbFe₂D_x (x = 3.0, 2.0).