Mg5Sb crystallizes in the trigonal R32 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent Mg(2), six equivalent Mg(1), and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with eighteen equivalent Mg(1)Mg10Sb2 cuboctahedra, edges with four equivalent Sb(1)Mg12 cuboctahedra, edges with six equivalent Mg(1)Mg10Sb2 cuboctahedra, edges with eight equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with four equivalent Sb(1)Mg12 cuboctahedra, faces with eight equivalent Mg(1)Mg10Sb2 cuboctahedra, and faces with eight equivalent Mg(2)Mg9Sb3 cuboctahedra. In the second Mg site, Mg(2) is bonded to three equivalent Mg(2), six equivalent Mg(1), and three equivalent Sb(1) atoms to form distorted MgMg9Sb3 cuboctahedra that share corners with six equivalent Sb(1)Mg12 cuboctahedra, corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra, faces with four equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with four equivalent Sb(1)Mg12 cuboctahedra, and faces with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra. Sb(1) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form SbMg12 cuboctahedra that share corners with six equivalent Sb(1)Mg12 cuboctahedra, corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg12 cuboctahedra, edges with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra, faces with eight equivalent Mg(2)Mg9Sb3 cuboctahedra, and faces with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra.
Mg5Sb crystallizes in the trigonal R32 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent Mg(2), six equivalent Mg(1), and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with eighteen equivalent Mg(1)Mg10Sb2 cuboctahedra, edges with four equivalent Sb(1)Mg12 cuboctahedra, edges with six equivalent Mg(1)Mg10Sb2 cuboctahedra, edges with eight equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with four equivalent Sb(1)Mg12 cuboctahedra, faces with eight equivalent Mg(1)Mg10Sb2 cuboctahedra, and faces with eight equivalent Mg(2)Mg9Sb3 cuboctahedra. All Mg(1)-Mg(2) bond lengths are 3.20 Å. All Mg(1)-Mg(1) bond lengths are 3.21 Å. Both Mg(1)-Sb(1) bond lengths are 3.20 Å. In the second Mg site, Mg(2) is bonded to three equivalent Mg(2), six equivalent Mg(1), and three equivalent Sb(1) atoms to form distorted MgMg9Sb3 cuboctahedra that share corners with six equivalent Sb(1)Mg12 cuboctahedra, corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra, faces with four equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with four equivalent Sb(1)Mg12 cuboctahedra, and faces with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra. All Mg(2)-Mg(2) bond lengths are 3.21 Å. All Mg(2)-Sb(1) bond lengths are 3.21 Å. Sb(1) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form SbMg12 cuboctahedra that share corners with six equivalent Sb(1)Mg12 cuboctahedra, corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg12 cuboctahedra, edges with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra, faces with eight equivalent Mg(2)Mg9Sb3 cuboctahedra, and faces with twelve equivalent Mg(1)Mg10Sb2 cuboctahedra.