Mg7Sb crystallizes in the hexagonal P-6m2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted linear geometry to two equivalent Mg(3), four equivalent Mg(2), and two equivalent Sb(1) atoms. In the second Mg site, Mg(2) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with four equivalent Mg(3)Mg12 cuboctahedra, corners with fourteen equivalent Mg(2)Mg10Sb2 cuboctahedra, edges with two equivalent Mg(3)Mg12 cuboctahedra, edges with four equivalent Mg(2)Mg10Sb2 cuboctahedra, edges with four equivalent Sb(1)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, and faces with six equivalent Mg(2)Mg10Sb2 cuboctahedra. In the third Mg site, Mg(3) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(3)Mg12 cuboctahedra, corners with twelve equivalent Mg(2)Mg10Sb2 cuboctahedra, edges with six equivalent Mg(2)Mg10Sb2 cuboctahedra, faces with two equivalent Mg(3)Mg12 cuboctahedra, faces with six equivalent Mg(2)Mg10Sb2 cuboctahedra, and faces with six equivalent Sb(1)Mg12 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, edges with twelve equivalent Mg(2)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, faces with six equivalent Mg(2)Mg10Sb2 cuboctahedra, and faces with six equivalent Mg(3)Mg12 cuboctahedra.
Mg7Sb crystallizes in the hexagonal P-6m2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted linear geometry to two equivalent Mg(3), four equivalent Mg(2), and two equivalent Sb(1) atoms. Both Mg(1)-Mg(3) bond lengths are 3.22 Å. All Mg(1)-Mg(2) bond lengths are 3.23 Å. Both Mg(1)-Sb(1) bond lengths are 3.16 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with four equivalent Mg(3)Mg12 cuboctahedra, corners with fourteen equivalent Mg(2)Mg10Sb2 cuboctahedra, edges with two equivalent Mg(3)Mg12 cuboctahedra, edges with four equivalent Mg(2)Mg10Sb2 cuboctahedra, edges with four equivalent Sb(1)Mg12 cuboctahedra, faces with two equivalent Mg(3)Mg12 cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, and faces with six equivalent Mg(2)Mg10Sb2 cuboctahedra. Both Mg(2)-Mg(3) bond lengths are 3.16 Å. There are two shorter (3.15 Å) and two longer (3.18 Å) Mg(2)-Mg(2) bond lengths. Both Mg(2)-Sb(1) bond lengths are 3.23 Å. In the third Mg site, Mg(3) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(3)Mg12 cuboctahedra, corners with twelve equivalent Mg(2)Mg10Sb2 cuboctahedra, edges with six equivalent Mg(2)Mg10Sb2 cuboctahedra, faces with two equivalent Mg(3)Mg12 cuboctahedra, faces with six equivalent Mg(2)Mg10Sb2 cuboctahedra, and faces with six equivalent Sb(1)Mg12 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, edges with twelve equivalent Mg(2)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, faces with six equivalent Mg(2)Mg10Sb2 cuboctahedra, and faces with six equivalent Mg(3)Mg12 cuboctahedra.