Mg2Cd crystallizes in the trigonal R32 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), six equivalent Mg(1), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with eighteen equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with four equivalent Mg(2)Mg6Cd6 cuboctahedra, edges with six equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with eight equivalent Cd(1)Mg9Cd3 cuboctahedra, faces with four equivalent Mg(2)Mg6Cd6 cuboctahedra, faces with eight equivalent Mg(1)Mg8Cd4 cuboctahedra, and faces with eight equivalent Cd(1)Mg9Cd3 cuboctahedra. In the second Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Cd(1) atoms to form MgMg6Cd6 cuboctahedra that share corners with six equivalent Mg(2)Mg6Cd6 cuboctahedra, corners with twelve equivalent Cd(1)Mg9Cd3 cuboctahedra, edges with six equivalent Mg(2)Mg6Cd6 cuboctahedra, edges with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with eight equivalent Cd(1)Mg9Cd3 cuboctahedra, and faces with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra. Cd(1) is bonded to three equivalent Mg(2), six equivalent Mg(1), and three equivalent Cd(1) atoms to form distorted CdMg9Cd3 cuboctahedra that share corners with six equivalent Mg(2)Mg6Cd6 cuboctahedra, corners with twelve equivalent Cd(1)Mg9Cd3 cuboctahedra, edges with six equivalent Cd(1)Mg9Cd3 cuboctahedra, edges with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(2)Mg6Cd6 cuboctahedra, faces with four equivalent Cd(1)Mg9Cd3 cuboctahedra, and faces with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra.
Mg2Cd crystallizes in the trigonal R32 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), six equivalent Mg(1), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with eighteen equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with four equivalent Mg(2)Mg6Cd6 cuboctahedra, edges with six equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with eight equivalent Cd(1)Mg9Cd3 cuboctahedra, faces with four equivalent Mg(2)Mg6Cd6 cuboctahedra, faces with eight equivalent Mg(1)Mg8Cd4 cuboctahedra, and faces with eight equivalent Cd(1)Mg9Cd3 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.12 Å. There are two shorter (3.11 Å) and four longer (3.13 Å) Mg(1)-Mg(1) bond lengths. There are two shorter (3.09 Å) and two longer (3.13 Å) Mg(1)-Cd(1) bond lengths. In the second Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Cd(1) atoms to form MgMg6Cd6 cuboctahedra that share corners with six equivalent Mg(2)Mg6Cd6 cuboctahedra, corners with twelve equivalent Cd(1)Mg9Cd3 cuboctahedra, edges with six equivalent Mg(2)Mg6Cd6 cuboctahedra, edges with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with eight equivalent Cd(1)Mg9Cd3 cuboctahedra, and faces with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra. All Mg(2)-Cd(1) bond lengths are 3.12 Å. Cd(1) is bonded to three equivalent Mg(2), six equivalent Mg(1), and three equivalent Cd(1) atoms to form distorted CdMg9Cd3 cuboctahedra that share corners with six equivalent Mg(2)Mg6Cd6 cuboctahedra, corners with twelve equivalent Cd(1)Mg9Cd3 cuboctahedra, edges with six equivalent Cd(1)Mg9Cd3 cuboctahedra, edges with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with four equivalent Mg(2)Mg6Cd6 cuboctahedra, faces with four equivalent Cd(1)Mg9Cd3 cuboctahedra, and faces with twelve equivalent Mg(1)Mg8Cd4 cuboctahedra. All Cd(1)-Cd(1) bond lengths are 3.12 Å.