Mg5Sb crystallizes in the hexagonal P-62m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted water-like geometry to four equivalent Mg(2) and two equivalent Sb(1) atoms. 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 nine equivalent Mg(2)Mg9Sb3 cuboctahedra, corners with nine equivalent Sb(1)Mg12 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with three equivalent Sb(1)Mg12 cuboctahedra, and faces with five equivalent Mg(2)Mg9Sb3 cuboctahedra. Sb(1) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form SbMg12 cuboctahedra that share corners with eighteen equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, and faces with six equivalent Mg(2)Mg9Sb3 cuboctahedra.
Mg5Sb crystallizes in the hexagonal P-62m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted water-like geometry to four equivalent Mg(2) and two equivalent Sb(1) atoms. All Mg(1)-Mg(2) bond lengths are 3.13 Å. Both Mg(1)-Sb(1) bond lengths are 3.16 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 nine equivalent Mg(2)Mg9Sb3 cuboctahedra, corners with nine equivalent Sb(1)Mg12 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with three equivalent Sb(1)Mg12 cuboctahedra, and faces with five equivalent Mg(2)Mg9Sb3 cuboctahedra. All Mg(2)-Mg(2) bond lengths are 3.29 Å. All Mg(2)-Sb(1) bond lengths are 3.29 Å. Sb(1) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form SbMg12 cuboctahedra that share corners with eighteen equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, and faces with six equivalent Mg(2)Mg9Sb3 cuboctahedra.