MgCd2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to three equivalent Mg(1), four equivalent Cd(2), and five equivalent Cd(1) atoms to form distorted MgMg3Cd9 cuboctahedra that share corners with six equivalent Mg(1)Mg3Cd9 cuboctahedra, corners with six equivalent Cd(2)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with four equivalent Mg(1)Mg3Cd9 cuboctahedra, edges with five equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with nine equivalent Cd(2)Mg4Cd8 cuboctahedra, faces with six equivalent Mg(1)Mg3Cd9 cuboctahedra, faces with six equivalent Cd(2)Mg4Cd8 cuboctahedra, and faces with eight equivalent Cd(1)Mg5Cd7 cuboctahedra. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to five equivalent Mg(1), three equivalent Cd(2), and four equivalent Cd(1) atoms to form distorted CdMg5Cd7 cuboctahedra that share corners with six equivalent Mg(1)Mg3Cd9 cuboctahedra, corners with six equivalent Cd(2)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with five equivalent Mg(1)Mg3Cd9 cuboctahedra, edges with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with seven equivalent Cd(2)Mg4Cd8 cuboctahedra, faces with five equivalent Cd(1)Mg5Cd7 cuboctahedra, faces with seven equivalent Cd(2)Mg4Cd8 cuboctahedra, and faces with eight equivalent Mg(1)Mg3Cd9 cuboctahedra. In the second Cd site, Cd(2) is bonded to four equivalent Mg(1), three equivalent Cd(1), and five equivalent Cd(2) atoms to form distorted CdMg4Cd8 cuboctahedra that share corners with six equivalent Mg(1)Mg3Cd9 cuboctahedra, corners with six equivalent Cd(2)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with two equivalent Cd(2)Mg4Cd8 cuboctahedra, edges with seven equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with nine equivalent Mg(1)Mg3Cd9 cuboctahedra, faces with six equivalent Mg(1)Mg3Cd9 cuboctahedra, faces with seven equivalent Cd(2)Mg4Cd8 cuboctahedra, and faces with seven equivalent Cd(1)Mg5Cd7 cuboctahedra.
MgCd2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to three equivalent Mg(1), four equivalent Cd(2), and five equivalent Cd(1) atoms to form distorted MgMg3Cd9 cuboctahedra that share corners with six equivalent Mg(1)Mg3Cd9 cuboctahedra, corners with six equivalent Cd(2)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with four equivalent Mg(1)Mg3Cd9 cuboctahedra, edges with five equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with nine equivalent Cd(2)Mg4Cd8 cuboctahedra, faces with six equivalent Mg(1)Mg3Cd9 cuboctahedra, faces with six equivalent Cd(2)Mg4Cd8 cuboctahedra, and faces with eight equivalent Cd(1)Mg5Cd7 cuboctahedra. There are two shorter (3.09 Å) and one longer (3.15 Å) Mg(1)-Mg(1) bond length. There are two shorter (3.05 Å) and two longer (3.10 Å) Mg(1)-Cd(2) bond lengths. There are a spread of Mg(1)-Cd(1) bond distances ranging from 3.07-3.19 Å. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to five equivalent Mg(1), three equivalent Cd(2), and four equivalent Cd(1) atoms to form distorted CdMg5Cd7 cuboctahedra that share corners with six equivalent Mg(1)Mg3Cd9 cuboctahedra, corners with six equivalent Cd(2)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with five equivalent Mg(1)Mg3Cd9 cuboctahedra, edges with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with seven equivalent Cd(2)Mg4Cd8 cuboctahedra, faces with five equivalent Cd(1)Mg5Cd7 cuboctahedra, faces with seven equivalent Cd(2)Mg4Cd8 cuboctahedra, and faces with eight equivalent Mg(1)Mg3Cd9 cuboctahedra. There are two shorter (3.07 Å) and one longer (3.13 Å) Cd(1)-Cd(2) bond length. There are two shorter (3.09 Å) and two longer (3.16 Å) Cd(1)-Cd(1) bond lengths. In the second Cd site, Cd(2) is bonded to four equivalent Mg(1), three equivalent Cd(1), and five equivalent Cd(2) atoms to form distorted CdMg4Cd8 cuboctahedra that share corners with six equivalent Mg(1)Mg3Cd9 cuboctahedra, corners with six equivalent Cd(2)Mg4Cd8 cuboctahedra, corners with six equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with two equivalent Cd(2)Mg4Cd8 cuboctahedra, edges with seven equivalent Cd(1)Mg5Cd7 cuboctahedra, edges with nine equivalent Mg(1)Mg3Cd9 cuboctahedra, faces with six equivalent Mg(1)Mg3Cd9 cuboctahedra, faces with seven equivalent Cd(2)Mg4Cd8 cuboctahedra, and faces with seven equivalent Cd(1)Mg5Cd7 cuboctahedra. There are a spread of Cd(2)-Cd(2) bond distances ranging from 3.09-3.18 Å.