DOE OSTI2020
MgTb5 crystallizes in the trigonal R32 space group. The structure is three-dimensional. Mg is bonded to twelve Tb atoms to form MgTb12 cuboctahedra that share corners with six equivalent MgTb12 cuboctahedra, corners with twelve TbTb9Mg3 cuboctahedra, edges with six equivalent MgTb12 cuboctahedra, edges with twelve TbTb10Mg2 cuboctahedra, and faces with twenty TbTb10Mg2 cuboctahedra. There are six shorter (3.46 Å) and six longer (3.56 Å) Mg–Tb bond lengths. There are eight inequivalent Tb sites. In the first Tb site, Tb is bonded to two equivalent Mg and ten Tb atoms to form distorted TbTb10Mg2 cuboctahedra that share corners with eighteen TbTb10Mg2 cuboctahedra, edges with four equivalent MgTb12 cuboctahedra, edges with fourteen TbTb10Mg2 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. There are a spread of Tb–Tb bond distances ranging from 3.44–3.63 Å. In the second Tb site, Tb is bonded to two equivalent Mg and ten Tb atoms to form distorted TbTb10Mg2 cuboctahedra that share corners with eighteen TbTb10Mg2 cuboctahedra, edges with four equivalent MgTb12 cuboctahedra, edges with fourteen TbTb9Mg3 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. There are a spread of Tb–Tb bond distances ranging from 3.44–3.63 Å. In the third Tb site, Tb is bonded to two equivalent Mg and ten Tb atoms to form distorted TbTb10Mg2 cuboctahedra that share corners with eighteen TbTb10Mg2 cuboctahedra, edges with four equivalent MgTb12 cuboctahedra, edges with fourteen TbTb10Mg2 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. There are a spread of Tb–Tb bond distances ranging from 3.44–3.63 Å. In the fourth Tb site, Tb is bonded to three equivalent Mg and nine Tb atoms to form TbTb9Mg3 cuboctahedra that share corners with six equivalent MgTb12 cuboctahedra, corners with twelve TbTb9Mg3 cuboctahedra, edges with eighteen TbTb10Mg2 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. There are one shorter (3.44 Å) and three longer (3.56 Å) Tb–Tb bond lengths. In the fifth Tb site, Tb is bonded to three equivalent Mg and nine Tb atoms to form TbTb9Mg3 cuboctahedra that share corners with six equivalent MgTb12 cuboctahedra, corners with twelve TbTb9Mg3 cuboctahedra, edges with eighteen TbTb10Mg2 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. All Tb–Mg bond lengths are 3.56 Å. There are a spread of Tb–Tb bond distances ranging from 3.44–3.56 Å. In the sixth Tb site, Tb is bonded to two equivalent Mg and ten Tb atoms to form distorted TbTb10Mg2 cuboctahedra that share corners with eighteen TbTb10Mg2 cuboctahedra, edges with four equivalent MgTb12 cuboctahedra, edges with fourteen TbTb9Mg3 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. There are one shorter (3.44 Å) and one longer (3.51 Å) Tb–Tb bond lengths. In the seventh Tb site, Tb is bonded to three equivalent Mg and nine Tb atoms to form TbTb9Mg3 cuboctahedra that share corners with six equivalent MgTb12 cuboctahedra, corners with twelve TbTb9Mg3 cuboctahedra, edges with eighteen TbTb10Mg2 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. All Tb–Mg bond lengths are 3.56 Å. There are one shorter (3.44 Å) and three longer (3.56 Å) Tb–Tb bond lengths. In the eighth Tb site, Tb is bonded to three equivalent Mg and nine Tb atoms to form TbTb9Mg3 cuboctahedra that share corners with six equivalent MgTb12 cuboctahedra, corners with twelve TbTb9Mg3 cuboctahedra, edges with eighteen TbTb10Mg2 cuboctahedra, faces with four equivalent MgTb12 cuboctahedra, and faces with sixteen TbTb10Mg2 cuboctahedra. All Tb–Mg bond lengths are 3.56 Å. The Tb–Tb bond length is 3.51 Å.