Mg6FeSb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Sb(1) atoms. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Fe(1) atoms to form distorted MgMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra, corners with six equivalent Mg(2)Mg10Fe2 cuboctahedra, edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra, and faces with six equivalent Sb(1)Mg10Fe2 cuboctahedra. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Sb(1) atoms. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra, corners with six equivalent Mg(4)Mg10Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra, edges with four equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra, and faces with six equivalent Fe(1)Mg10Sb2 cuboctahedra. Fe(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Sb(1) atoms to form FeMg10Sb2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra, corners with six equivalent Fe(1)Mg10Sb2 cuboctahedra, edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra, edges with four equivalent Sb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Sb2 cuboctahedra. Sb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Fe(1) atoms to form SbMg10Fe2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra, corners with six equivalent Sb(1)Mg10Fe2 cuboctahedra, edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra, edges with four equivalent Fe(1)Mg10Sb2 cuboctahedra, faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Fe2 cuboctahedra.
Mg6FeSb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Sb(1) atoms. There is one shorter (3.04 Å) and one longer (3.23 Å) Mg(1)-Mg(1) bond length. There is one shorter (3.05 Å) and one longer (3.08 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.01 Å. Both Mg(1)-Mg(4) bond lengths are 3.01 Å. There is one shorter (3.04 Å) and one longer (3.09 Å) Mg(1)-Fe(1) bond length. Both Mg(1)-Sb(1) bond lengths are 3.08 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Fe(1) atoms to form distorted MgMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra, corners with six equivalent Mg(2)Mg10Fe2 cuboctahedra, edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra, and faces with six equivalent Sb(1)Mg10Fe2 cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 2.99 Å. All Mg(2)-Mg(3) bond lengths are 3.04 Å. Both Mg(2)-Fe(1) bond lengths are 3.13 Å. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Sb(1) atoms. There is one shorter (3.04 Å) and one longer (3.09 Å) Mg(3)-Mg(4) bond length. Both Mg(3)-Fe(1) bond lengths are 2.96 Å. There is one shorter (2.89 Å) and one longer (3.23 Å) Mg(3)-Sb(1) bond length. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Sb(1) atoms to form distorted MgMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra, corners with six equivalent Mg(4)Mg10Sb2 cuboctahedra, edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra, edges with four equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra, and faces with six equivalent Fe(1)Mg10Sb2 cuboctahedra. Both Mg(4)-Sb(1) bond lengths are 3.13 Å. Fe(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Sb(1) atoms to form FeMg10Sb2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra, corners with six equivalent Fe(1)Mg10Sb2 cuboctahedra, edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra, edges with four equivalent Sb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Sb2 cuboctahedra. Both Fe(1)-Sb(1) bond lengths are 2.93 Å. Sb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Fe(1) atoms to form SbMg10Fe2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Sb2 cuboctahedra, corners with six equivalent Sb(1)Mg10Fe2 cuboctahedra, edges with two equivalent Mg(4)Mg10Sb2 cuboctahedra, edges with four equivalent Fe(1)Mg10Sb2 cuboctahedra, faces with two equivalent Mg(4)Mg10Sb2 cuboctahedra, faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra, faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Fe2 cuboctahedra.