DOE OSTI2020
TbMg3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to eight Mg and four equivalent Tb atoms to form distorted MgTb4Mg8 cuboctahedra that share corners with four equivalent TbMg12 cuboctahedra, corners with fourteen MgTb4Mg8 cuboctahedra, edges with six equivalent TbMg12 cuboctahedra, edges with twelve MgTb4Mg8 cuboctahedra, faces with four equivalent TbMg12 cuboctahedra, and faces with sixteen MgTb4Mg8 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.21–3.43 Å. There are two shorter (3.26 Å) and two longer (3.35 Å) Mg–Tb bond lengths. In the second Mg site, Mg is bonded to eight Mg and four equivalent Tb atoms to form distorted MgTb4Mg8 cuboctahedra that share corners with four equivalent TbMg12 cuboctahedra, corners with fourteen MgTb4Mg8 cuboctahedra, edges with six equivalent TbMg12 cuboctahedra, edges with twelve MgTb4Mg8 cuboctahedra, faces with four equivalent TbMg12 cuboctahedra, and faces with sixteen MgTb4Mg8 cuboctahedra. Both Mg–Mg bond lengths are 3.21 Å. There are two shorter (3.26 Å) and two longer (3.35 Å) Mg–Tb bond lengths. Tb is bonded to twelve Mg atoms to form TbMg12 cuboctahedra that share corners with six equivalent TbMg12 cuboctahedra, corners with twelve MgTb4Mg8 cuboctahedra, edges with eighteen MgTb4Mg8 cuboctahedra, faces with eight equivalent TbMg12 cuboctahedra, and faces with twelve MgTb4Mg8 cuboctahedra.