MgCd2 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded to four equivalent Mg(1), two equivalent Cd(2), and six equivalent Cd(1) atoms to form distorted MgMg4Cd8 cuboctahedra that share corners with six equivalent Mg(1)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(2)Mg2Cd10 cuboctahedra, corners with six equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with seven equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with eleven equivalent Cd(2)Mg2Cd10 cuboctahedra, faces with four equivalent Cd(2)Mg2Cd10 cuboctahedra, faces with six equivalent Cd(1)Mg6Cd6 cuboctahedra, and faces with ten equivalent Mg(1)Mg4Cd8 cuboctahedra. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to six equivalent Mg(1), two equivalent Cd(1), and four equivalent Cd(2) atoms to form distorted CdMg6Cd6 cuboctahedra that share corners with six equivalent Mg(1)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(2)Mg2Cd10 cuboctahedra, corners with six equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with three equivalent Cd(2)Mg2Cd10 cuboctahedra, edges with seven equivalent Mg(1)Mg4Cd8 cuboctahedra, edges with eight equivalent Cd(1)Mg6Cd6 cuboctahedra, faces with six equivalent Mg(1)Mg4Cd8 cuboctahedra, faces with six equivalent Cd(1)Mg6Cd6 cuboctahedra, and faces with eight equivalent Cd(2)Mg2Cd10 cuboctahedra. In the second Cd site, Cd(2) is bonded to two equivalent Mg(1), four equivalent Cd(1), and six equivalent Cd(2) atoms to form distorted CdMg2Cd10 cuboctahedra that share corners with six equivalent Mg(1)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(2)Mg2Cd10 cuboctahedra, corners with six equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with three equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with four equivalent Cd(2)Mg2Cd10 cuboctahedra, edges with eleven equivalent Mg(1)Mg4Cd8 cuboctahedra, faces with four equivalent Mg(1)Mg4Cd8 cuboctahedra, faces with eight equivalent Cd(2)Mg2Cd10 cuboctahedra, and faces with eight equivalent Cd(1)Mg6Cd6 cuboctahedra.
MgCd2 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded to four equivalent Mg(1), two equivalent Cd(2), and six equivalent Cd(1) atoms to form distorted MgMg4Cd8 cuboctahedra that share corners with six equivalent Mg(1)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(2)Mg2Cd10 cuboctahedra, corners with six equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with seven equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with eleven equivalent Cd(2)Mg2Cd10 cuboctahedra, faces with four equivalent Cd(2)Mg2Cd10 cuboctahedra, faces with six equivalent Cd(1)Mg6Cd6 cuboctahedra, and faces with ten equivalent Mg(1)Mg4Cd8 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 3.13 Å. Both Mg(1)-Cd(2) bond lengths are 3.07 Å. There are four shorter (3.07 Å) and two longer (3.10 Å) Mg(1)-Cd(1) bond lengths. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to six equivalent Mg(1), two equivalent Cd(1), and four equivalent Cd(2) atoms to form distorted CdMg6Cd6 cuboctahedra that share corners with six equivalent Mg(1)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(2)Mg2Cd10 cuboctahedra, corners with six equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with three equivalent Cd(2)Mg2Cd10 cuboctahedra, edges with seven equivalent Mg(1)Mg4Cd8 cuboctahedra, edges with eight equivalent Cd(1)Mg6Cd6 cuboctahedra, faces with six equivalent Mg(1)Mg4Cd8 cuboctahedra, faces with six equivalent Cd(1)Mg6Cd6 cuboctahedra, and faces with eight equivalent Cd(2)Mg2Cd10 cuboctahedra. Both Cd(1)-Cd(1) bond lengths are 3.13 Å. There are two shorter (3.11 Å) and two longer (3.17 Å) Cd(1)-Cd(2) bond lengths. In the second Cd site, Cd(2) is bonded to two equivalent Mg(1), four equivalent Cd(1), and six equivalent Cd(2) atoms to form distorted CdMg2Cd10 cuboctahedra that share corners with six equivalent Mg(1)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(2)Mg2Cd10 cuboctahedra, corners with six equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with three equivalent Cd(1)Mg6Cd6 cuboctahedra, edges with four equivalent Cd(2)Mg2Cd10 cuboctahedra, edges with eleven equivalent Mg(1)Mg4Cd8 cuboctahedra, faces with four equivalent Mg(1)Mg4Cd8 cuboctahedra, faces with eight equivalent Cd(2)Mg2Cd10 cuboctahedra, and faces with eight equivalent Cd(1)Mg6Cd6 cuboctahedra. There are four shorter (3.11 Å) and two longer (3.13 Å) Cd(2)-Cd(2) bond lengths.