Mg3Cd crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), six equivalent Mg(2), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with four equivalent Cd(1)Mg10Cd2 cuboctahedra, corners with fourteen equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with two equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with four equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra, faces with two equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with six equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra. In the second Mg site, Mg(2) is bonded to three equivalent Mg(1), six equivalent Mg(2), and three equivalent Cd(1) atoms to form distorted MgMg9Cd3 cuboctahedra that share corners with eighteen equivalent Mg(2)Mg9Cd3 cuboctahedra, edges with six equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with six equivalent Mg(2)Mg9Cd3 cuboctahedra, edges with six equivalent Cd(1)Mg10Cd2 cuboctahedra, faces with six equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with six equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(2)Mg9Cd3 cuboctahedra. Cd(1) is bonded to four equivalent Mg(1), six equivalent Mg(2), and two equivalent Cd(1) atoms to form distorted CdMg10Cd2 cuboctahedra that share corners with four equivalent Mg(1)Mg8Cd4 cuboctahedra, corners with fourteen equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with two equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra, faces with two equivalent Cd(1)Mg10Cd2 cuboctahedra, faces with six equivalent Mg(1)Mg8Cd4 cuboctahedra, and faces with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra.
Mg3Cd crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), six equivalent Mg(2), and four equivalent Cd(1) atoms to form distorted MgMg8Cd4 cuboctahedra that share corners with four equivalent Cd(1)Mg10Cd2 cuboctahedra, corners with fourteen equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with two equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with four equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra, faces with two equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with six equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 3.19 Å. There are two shorter (3.09 Å) and four longer (3.14 Å) Mg(1)-Mg(2) bond lengths. There are two shorter (3.08 Å) and two longer (3.18 Å) Mg(1)-Cd(1) bond lengths. In the second Mg site, Mg(2) is bonded to three equivalent Mg(1), six equivalent Mg(2), and three equivalent Cd(1) atoms to form distorted MgMg9Cd3 cuboctahedra that share corners with eighteen equivalent Mg(2)Mg9Cd3 cuboctahedra, edges with six equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with six equivalent Mg(2)Mg9Cd3 cuboctahedra, edges with six equivalent Cd(1)Mg10Cd2 cuboctahedra, faces with six equivalent Mg(1)Mg8Cd4 cuboctahedra, faces with six equivalent Cd(1)Mg10Cd2 cuboctahedra, and faces with eight equivalent Mg(2)Mg9Cd3 cuboctahedra. There are four shorter (3.13 Å) and two longer (3.19 Å) Mg(2)-Mg(2) bond lengths. There are two shorter (3.07 Å) and one longer (3.14 Å) Mg(2)-Cd(1) bond length. Cd(1) is bonded to four equivalent Mg(1), six equivalent Mg(2), and two equivalent Cd(1) atoms to form distorted CdMg10Cd2 cuboctahedra that share corners with four equivalent Mg(1)Mg8Cd4 cuboctahedra, corners with fourteen equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with two equivalent Cd(1)Mg10Cd2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cd4 cuboctahedra, edges with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra, faces with two equivalent Cd(1)Mg10Cd2 cuboctahedra, faces with six equivalent Mg(1)Mg8Cd4 cuboctahedra, and faces with twelve equivalent Mg(2)Mg9Cd3 cuboctahedra. Both Cd(1)-Cd(1) bond lengths are 3.19 Å.