Mg2Sc crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), four equivalent Mg(2), and six equivalent Sc(1) atoms to form MgMg6Sc6 cuboctahedra that share corners with six equivalent Mg(2)Mg10Sc2 cuboctahedra, corners with six equivalent Mg(1)Mg6Sc6 cuboctahedra, corners with six equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with three equivalent Mg(2)Mg10Sc2 cuboctahedra, edges with seven equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with eight equivalent Mg(1)Mg6Sc6 cuboctahedra, faces with six equivalent Mg(1)Mg6Sc6 cuboctahedra, faces with six equivalent Sc(1)Mg8Sc4 cuboctahedra, and faces with eight equivalent Mg(2)Mg10Sc2 cuboctahedra. In the second Mg site, Mg(2) is bonded to four equivalent Mg(1), six equivalent Mg(2), and two equivalent Sc(1) atoms to form MgMg10Sc2 cuboctahedra that share corners with six equivalent Mg(2)Mg10Sc2 cuboctahedra, corners with six equivalent Mg(1)Mg6Sc6 cuboctahedra, corners with six equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with three equivalent Mg(1)Mg6Sc6 cuboctahedra, edges with four equivalent Mg(2)Mg10Sc2 cuboctahedra, edges with eleven equivalent Sc(1)Mg8Sc4 cuboctahedra, faces with four equivalent Sc(1)Mg8Sc4 cuboctahedra, faces with eight equivalent Mg(2)Mg10Sc2 cuboctahedra, and faces with eight equivalent Mg(1)Mg6Sc6 cuboctahedra. Sc(1) is bonded to two equivalent Mg(2), six equivalent Mg(1), and four equivalent Sc(1) atoms to form ScMg8Sc4 cuboctahedra that share corners with six equivalent Mg(2)Mg10Sc2 cuboctahedra, corners with six equivalent Mg(1)Mg6Sc6 cuboctahedra, corners with six equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with seven equivalent Mg(1)Mg6Sc6 cuboctahedra, edges with eleven equivalent Mg(2)Mg10Sc2 cuboctahedra, faces with four equivalent Mg(2)Mg10Sc2 cuboctahedra, faces with six equivalent Mg(1)Mg6Sc6 cuboctahedra, and faces with ten equivalent Sc(1)Mg8Sc4 cuboctahedra.
Mg2Sc crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), four equivalent Mg(2), and six equivalent Sc(1) atoms to form MgMg6Sc6 cuboctahedra that share corners with six equivalent Mg(2)Mg10Sc2 cuboctahedra, corners with six equivalent Mg(1)Mg6Sc6 cuboctahedra, corners with six equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with three equivalent Mg(2)Mg10Sc2 cuboctahedra, edges with seven equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with eight equivalent Mg(1)Mg6Sc6 cuboctahedra, faces with six equivalent Mg(1)Mg6Sc6 cuboctahedra, faces with six equivalent Sc(1)Mg8Sc4 cuboctahedra, and faces with eight equivalent Mg(2)Mg10Sc2 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 3.27 Å. There are two shorter (3.17 Å) and two longer (3.20 Å) Mg(1)-Mg(2) bond lengths. There are four shorter (3.18 Å) and two longer (3.21 Å) Mg(1)-Sc(1) bond lengths. In the second Mg site, Mg(2) is bonded to four equivalent Mg(1), six equivalent Mg(2), and two equivalent Sc(1) atoms to form MgMg10Sc2 cuboctahedra that share corners with six equivalent Mg(2)Mg10Sc2 cuboctahedra, corners with six equivalent Mg(1)Mg6Sc6 cuboctahedra, corners with six equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with three equivalent Mg(1)Mg6Sc6 cuboctahedra, edges with four equivalent Mg(2)Mg10Sc2 cuboctahedra, edges with eleven equivalent Sc(1)Mg8Sc4 cuboctahedra, faces with four equivalent Sc(1)Mg8Sc4 cuboctahedra, faces with eight equivalent Mg(2)Mg10Sc2 cuboctahedra, and faces with eight equivalent Mg(1)Mg6Sc6 cuboctahedra. There are four shorter (3.17 Å) and two longer (3.27 Å) Mg(2)-Mg(2) bond lengths. Both Mg(2)-Sc(1) bond lengths are 3.21 Å. Sc(1) is bonded to two equivalent Mg(2), six equivalent Mg(1), and four equivalent Sc(1) atoms to form ScMg8Sc4 cuboctahedra that share corners with six equivalent Mg(2)Mg10Sc2 cuboctahedra, corners with six equivalent Mg(1)Mg6Sc6 cuboctahedra, corners with six equivalent Sc(1)Mg8Sc4 cuboctahedra, edges with seven equivalent Mg(1)Mg6Sc6 cuboctahedra, edges with eleven equivalent Mg(2)Mg10Sc2 cuboctahedra, faces with four equivalent Mg(2)Mg10Sc2 cuboctahedra, faces with six equivalent Mg(1)Mg6Sc6 cuboctahedra, and faces with ten equivalent Sc(1)Mg8Sc4 cuboctahedra. There are two shorter (3.20 Å) and two longer (3.27 Å) Sc(1)-Sc(1) bond lengths.