Mg2Y 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(2), four equivalent Mg(1), and six equivalent Y(1) atoms to form MgY6Mg6 cuboctahedra that share corners with six equivalent Mg(2)Y4Mg8 cuboctahedra, corners with six equivalent Mg(1)Y6Mg6 cuboctahedra, corners with six equivalent Y(1)Y2Mg10 cuboctahedra, edges with seven equivalent Y(1)Y2Mg10 cuboctahedra, edges with eleven equivalent Mg(2)Y4Mg8 cuboctahedra, faces with four equivalent Mg(2)Y4Mg8 cuboctahedra, faces with six equivalent Y(1)Y2Mg10 cuboctahedra, and faces with ten equivalent Mg(1)Y6Mg6 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), six equivalent Mg(2), and four equivalent Y(1) atoms to form MgY4Mg8 cuboctahedra that share corners with six equivalent Mg(2)Y4Mg8 cuboctahedra, corners with six equivalent Mg(1)Y6Mg6 cuboctahedra, corners with six equivalent Y(1)Y2Mg10 cuboctahedra, edges with three equivalent Y(1)Y2Mg10 cuboctahedra, edges with four equivalent Mg(2)Y4Mg8 cuboctahedra, edges with eleven equivalent Mg(1)Y6Mg6 cuboctahedra, faces with four equivalent Mg(1)Y6Mg6 cuboctahedra, faces with eight equivalent Mg(2)Y4Mg8 cuboctahedra, and faces with eight equivalent Y(1)Y2Mg10 cuboctahedra. Y(1) is bonded to four equivalent Mg(2), six equivalent Mg(1), and two equivalent Y(1) atoms to form YY2Mg10 cuboctahedra that share corners with six equivalent Mg(2)Y4Mg8 cuboctahedra, corners with six equivalent Mg(1)Y6Mg6 cuboctahedra, corners with six equivalent Y(1)Y2Mg10 cuboctahedra, edges with three equivalent Mg(2)Y4Mg8 cuboctahedra, edges with seven equivalent Mg(1)Y6Mg6 cuboctahedra, edges with eight equivalent Y(1)Y2Mg10 cuboctahedra, faces with six equivalent Mg(1)Y6Mg6 cuboctahedra, faces with six equivalent Y(1)Y2Mg10 cuboctahedra, and faces with eight equivalent Mg(2)Y4Mg8 cuboctahedra.
Mg2Y 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(2), four equivalent Mg(1), and six equivalent Y(1) atoms to form MgY6Mg6 cuboctahedra that share corners with six equivalent Mg(2)Y4Mg8 cuboctahedra, corners with six equivalent Mg(1)Y6Mg6 cuboctahedra, corners with six equivalent Y(1)Y2Mg10 cuboctahedra, edges with seven equivalent Y(1)Y2Mg10 cuboctahedra, edges with eleven equivalent Mg(2)Y4Mg8 cuboctahedra, faces with four equivalent Mg(2)Y4Mg8 cuboctahedra, faces with six equivalent Y(1)Y2Mg10 cuboctahedra, and faces with ten equivalent Mg(1)Y6Mg6 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.27 Å. There are two shorter (3.35 Å) and two longer (3.39 Å) Mg(1)-Mg(1) bond lengths. There are two shorter (3.31 Å) and four longer (3.32 Å) Mg(1)-Y(1) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), six equivalent Mg(2), and four equivalent Y(1) atoms to form MgY4Mg8 cuboctahedra that share corners with six equivalent Mg(2)Y4Mg8 cuboctahedra, corners with six equivalent Mg(1)Y6Mg6 cuboctahedra, corners with six equivalent Y(1)Y2Mg10 cuboctahedra, edges with three equivalent Y(1)Y2Mg10 cuboctahedra, edges with four equivalent Mg(2)Y4Mg8 cuboctahedra, edges with eleven equivalent Mg(1)Y6Mg6 cuboctahedra, faces with four equivalent Mg(1)Y6Mg6 cuboctahedra, faces with eight equivalent Mg(2)Y4Mg8 cuboctahedra, and faces with eight equivalent Y(1)Y2Mg10 cuboctahedra. There are two shorter (3.35 Å) and four longer (3.36 Å) Mg(2)-Mg(2) bond lengths. There are two shorter (3.36 Å) and two longer (3.40 Å) Mg(2)-Y(1) bond lengths. Y(1) is bonded to four equivalent Mg(2), six equivalent Mg(1), and two equivalent Y(1) atoms to form YY2Mg10 cuboctahedra that share corners with six equivalent Mg(2)Y4Mg8 cuboctahedra, corners with six equivalent Mg(1)Y6Mg6 cuboctahedra, corners with six equivalent Y(1)Y2Mg10 cuboctahedra, edges with three equivalent Mg(2)Y4Mg8 cuboctahedra, edges with seven equivalent Mg(1)Y6Mg6 cuboctahedra, edges with eight equivalent Y(1)Y2Mg10 cuboctahedra, faces with six equivalent Mg(1)Y6Mg6 cuboctahedra, faces with six equivalent Y(1)Y2Mg10 cuboctahedra, and faces with eight equivalent Mg(2)Y4Mg8 cuboctahedra. Both Y(1)-Y(1) bond lengths are 3.35 Å.