Mg3Cd crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with eight equivalent Cd(1)Mg10Cd2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with two equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with four equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with four equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with eight equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(2)Mg8Cd4 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with eight equivalent Mg(3)Mg10Cd2 cuboctahedra, corners with ten equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with two equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with four equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with eight equivalent Cd(1)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(2)Mg8Cd4 cuboctahedra, faces with four equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Cd4 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cd(1) atoms to form distorted MgMg10Cd2 cuboctahedra that share corners with eight equivalent Mg(2)Mg8Cd4 cuboctahedra, corners with ten equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with two equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with four equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(2)Mg8Cd4 cuboctahedra, and faces with eight equivalent Cd(1)Mg10Cd2 cuboctahedra. Cd(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cd(1) atoms to form distorted CdMg10Cd2 cuboctahedra that share corners with eight equivalent Mg(1)Mg8Cd4 cuboctahedra, corners with ten equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with two equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with eight equivalent Mg(2)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(2)Mg8Cd4 cuboctahedra, faces with four equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(3)Mg10Cd2 cuboctahedra.
Mg3Cd crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with eight equivalent Cd(1)Mg10Cd2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with two equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with four equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with four equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with eight equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(2)Mg8Cd4 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 3.21 Å. Both Mg(1)-Mg(2) bond lengths are 3.10 Å. All Mg(1)-Mg(3) bond lengths are 3.11 Å. There are two shorter (3.11 Å) and two longer (3.13 Å) Mg(1)-Cd(1) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with eight equivalent Mg(3)Mg10Cd2 cuboctahedra, corners with ten equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with two equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with four equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with eight equivalent Cd(1)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(2)Mg8Cd4 cuboctahedra, faces with four equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Cd4 cuboctahedra. Both Mg(2)-Mg(2) bond lengths are 3.21 Å. There are two shorter (3.11 Å) and two longer (3.13 Å) Mg(2)-Mg(3) bond lengths. All Mg(2)-Cd(1) bond lengths are 3.11 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cd(1) atoms to form distorted MgMg10Cd2 cuboctahedra that share corners with eight equivalent Mg(2)Mg8Cd4 cuboctahedra, corners with ten equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with two equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(2)Mg8Cd4 cuboctahedra, edges with four equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(3)Mg10Cd2 cuboctahedra, faces with four equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(2)Mg8Cd4 cuboctahedra, and faces with eight equivalent Cd(1)Mg10Cd2 cuboctahedra. Both Mg(3)-Mg(3) bond lengths are 3.21 Å. Both Mg(3)-Cd(1) bond lengths are 3.08 Å. Cd(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cd(1) atoms to form distorted CdMg10Cd2 cuboctahedra that share corners with eight equivalent Mg(1)Mg8Cd4 cuboctahedra, corners with ten equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with two equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(3)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with eight equivalent Mg(2)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(2)Mg8Cd4 cuboctahedra, faces with four equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(3)Mg10Cd2 cuboctahedra. Both Cd(1)-Cd(1) bond lengths are 3.21 Å.