Mg14CuSb crystallizes in the hexagonal P-6m2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Sb(1)Mg12 cuboctahedra, corners with six equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg12 cuboctahedra, edges with four equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with eight equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Cu(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Mg10Cu2 cuboctahedra, and faces with ten equivalent Mg(3)Mg10CuSb cuboctahedra. In the second Mg site, Mg(2) is bonded in a distorted linear geometry to two equivalent Mg(4), four equivalent Mg(3), and two equivalent Sb(1) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(3), one Cu(1), and one Sb(1) atom to form distorted MgMg10CuSb cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra, corners with fourteen equivalent Mg(3)Mg10CuSb cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Cu(1)Mg12 cuboctahedra, edges with two equivalent Sb(1)Mg12 cuboctahedra, edges with four equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg10CuSb cuboctahedra,  a faceface with one Cu(1)Mg12 cuboctahedra,  a faceface with one Sb(1)Mg12 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with five equivalent Mg(1)Mg10Cu2 cuboctahedra, and faces with six equivalent Mg(3)Mg10CuSb cuboctahedra. In the fourth Mg site, Mg(4) is bonded to three equivalent Mg(1), three equivalent Mg(2), and six equivalent Mg(3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra, corners with twelve equivalent Mg(3)Mg10CuSb cuboctahedra, edges with six equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with six equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with three equivalent Mg(1)Mg10Cu2 cuboctahedra, faces with three equivalent Cu(1)Mg12 cuboctahedra, faces with three equivalent Sb(1)Mg12 cuboctahedra, and faces with six equivalent Mg(3)Mg10CuSb cuboctahedra. Cu(1) is bonded to six equivalent Mg(1) and six equivalent Mg(3) atoms to form CuMg12 cuboctahedra that share corners with six equivalent Cu(1)Mg12 cuboctahedra, edges with six equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with twelve equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, faces with six equivalent Mg(1)Mg10Cu2 cuboctahedra, faces with six equivalent Mg(3)Mg10CuSb cuboctahedra, and faces with six equivalent Mg(4)Mg12 cuboctahedra. Sb(1) is bonded to six equivalent Mg(2) and six equivalent Mg(3) atoms to form SbMg12 cuboctahedra that share corners with six equivalent Sb(1)Mg12 cuboctahedra, corners with twelve equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with twelve equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Cu(1)Mg12 cuboctahedra, faces with six equivalent Mg(3)Mg10CuSb cuboctahedra, and faces with six equivalent Mg(4)Mg12 cuboctahedra.
Mg14CuSb crystallizes in the hexagonal P-6m2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Sb(1)Mg12 cuboctahedra, corners with six equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg12 cuboctahedra, edges with four equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, edges with eight equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Cu(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Mg10Cu2 cuboctahedra, and faces with ten equivalent Mg(3)Mg10CuSb cuboctahedra. Both Mg(1)-Mg(4) bond lengths are 3.14 Å. There are two shorter (3.12 Å) and two longer (3.16 Å) Mg(1)-Mg(1) bond lengths. All Mg(1)-Mg(3) bond lengths are 3.07 Å. Both Mg(1)-Cu(1) bond lengths are 3.14 Å. In the second Mg site, Mg(2) is bonded in a distorted linear geometry to two equivalent Mg(4), four equivalent Mg(3), and two equivalent Sb(1) atoms. Both Mg(2)-Mg(4) bond lengths are 3.15 Å. All Mg(2)-Mg(3) bond lengths are 3.25 Å. Both Mg(2)-Sb(1) bond lengths are 3.14 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(3), one Cu(1), and one Sb(1) atom to form distorted MgMg10CuSb cuboctahedra that share corners with four equivalent Mg(4)Mg12 cuboctahedra, corners with fourteen equivalent Mg(3)Mg10CuSb cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Cu(1)Mg12 cuboctahedra, edges with two equivalent Sb(1)Mg12 cuboctahedra, edges with four equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg10CuSb cuboctahedra,  a faceface with one Cu(1)Mg12 cuboctahedra,  a faceface with one Sb(1)Mg12 cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with five equivalent Mg(1)Mg10Cu2 cuboctahedra, and faces with six equivalent Mg(3)Mg10CuSb cuboctahedra. Both Mg(3)-Mg(4) bond lengths are 3.14 Å. There are two shorter (3.10 Å) and two longer (3.18 Å) Mg(3)-Mg(3) bond lengths. The Mg(3)-Cu(1) bond length is 3.05 Å. The Mg(3)-Sb(1) bond length is 3.23 Å. In the fourth Mg site, Mg(4) is bonded to three equivalent Mg(1), three equivalent Mg(2), and six equivalent Mg(3) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(4)Mg12 cuboctahedra, corners with twelve equivalent Mg(3)Mg10CuSb cuboctahedra, edges with six equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with six equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Mg(4)Mg12 cuboctahedra, faces with three equivalent Mg(1)Mg10Cu2 cuboctahedra, faces with three equivalent Cu(1)Mg12 cuboctahedra, faces with three equivalent Sb(1)Mg12 cuboctahedra, and faces with six equivalent Mg(3)Mg10CuSb cuboctahedra. Cu(1) is bonded to six equivalent Mg(1) and six equivalent Mg(3) atoms to form CuMg12 cuboctahedra that share corners with six equivalent Cu(1)Mg12 cuboctahedra, edges with six equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with twelve equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Sb(1)Mg12 cuboctahedra, faces with six equivalent Mg(1)Mg10Cu2 cuboctahedra, faces with six equivalent Mg(3)Mg10CuSb cuboctahedra, and faces with six equivalent Mg(4)Mg12 cuboctahedra. Sb(1) is bonded to six equivalent Mg(2) and six equivalent Mg(3) atoms to form SbMg12 cuboctahedra that share corners with six equivalent Sb(1)Mg12 cuboctahedra, corners with twelve equivalent Mg(1)Mg10Cu2 cuboctahedra, edges with twelve equivalent Mg(3)Mg10CuSb cuboctahedra, faces with two equivalent Cu(1)Mg12 cuboctahedra, faces with six equivalent Mg(3)Mg10CuSb cuboctahedra, and faces with six equivalent Mg(4)Mg12 cuboctahedra.