Mg6FeSb crystallizes in the orthorhombic Amm2 space group. There are nine inequivalent Mg sites. In the first Mg site, Mg(1) is bonded 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 to form distorted MgMg8Fe2Sb2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra. In the second Mg site, Mg(1) is bonded 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 to form distorted MgMg8Fe2Sb2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with ten Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra. In the third Mg site, Mg(2) 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 fourth Mg site, Mg(2) 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 fifth Mg site, Mg(3) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(2,2,2,2); and two equivalent Fe(1) atoms to form distorted MgMg10Fe2 cuboctahedra that share corners with six equivalent Mg(3)Mg10Fe2 cuboctahedra; edges with four equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with eight Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra; and faces with six equivalent Sb(1)Mg10Fe2 cuboctahedra. In the sixth Mg site, Mg(4) is bonded in a distorted water-like geometry to two equivalent Mg(3); four Mg(1,1); four Mg(2,2,2,2); and two equivalent Sb(1) atoms. In the seventh Mg site, Mg(1) is bonded 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 to form distorted MgMg8Fe2Sb2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra. In the eighth Mg site, Mg(2) 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 ninth Mg site, Mg(2) 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. Fe(1) is bonded to two equivalent Mg(3); four Mg(1,1,1); four Mg(2,2); and two equivalent Sb(1) atoms to form FeMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with six equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with eight Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; edges with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra. Sb(1) is bonded to two equivalent Mg(4); four Mg(1,1,1); four Mg(2,2); and two equivalent Fe(1) atoms to form SbMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with six equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with eight Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; and faces with six equivalent Mg(3)Mg10Fe2 cuboctahedra.
Mg6FeSb crystallizes in the orthorhombic Amm2 space group. There are nine inequivalent Mg sites. In the first Mg site, Mg(1) is bonded 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 to form distorted MgMg8Fe2Sb2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra. There is one shorter (3.02 Å) and one longer (3.07 Å) Mg(1)-Mg(1) bond length. Both Mg(1)-Mg(2) bond lengths are 3.01 Å. Both Mg(1)-Mg(3) bond lengths are 3.01 Å. Both Mg(1)-Mg(4) bond lengths are 2.99 Å. There is one shorter (3.04 Å) and one longer (3.05 Å) Mg(1)-Fe(1) bond length. There is one shorter (3.04 Å) and one longer (3.05 Å) Mg(1)-Sb(1) bond length. In the second Mg site, Mg(1) is bonded 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 to form distorted MgMg8Fe2Sb2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with ten Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.01 Å. Both Mg(1)-Mg(3) bond lengths are 3.01 Å. Both Mg(1)-Mg(4) bond lengths are 2.99 Å. There is one shorter (3.04 Å) and one longer (3.05 Å) Mg(1)-Fe(1) bond length. There is one shorter (3.04 Å) and one longer (3.05 Å) Mg(1)-Sb(1) bond length. In the third Mg site, Mg(2) 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 (2.83 Å) and one longer (3.26 Å) Mg(2)-Mg(2) bond length. There is one shorter (2.89 Å) and one longer (3.20 Å) Mg(2)-Mg(3) bond length. There is one shorter (2.97 Å) and one longer (3.12 Å) Mg(2)-Mg(4) bond length. Both Mg(2)-Fe(1) bond lengths are 2.93 Å. Both Mg(2)-Sb(1) bond lengths are 3.05 Å. In the fourth Mg site, Mg(2) 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 (2.89 Å) and one longer (3.20 Å) Mg(2)-Mg(3) bond length. There is one shorter (2.97 Å) and one longer (3.12 Å) Mg(2)-Mg(4) bond length. Both Mg(2)-Fe(1) bond lengths are 2.93 Å. Both Mg(2)-Sb(1) bond lengths are 3.05 Å. In the fifth Mg site, Mg(3) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(2,2,2,2); and two equivalent Fe(1) atoms to form distorted MgMg10Fe2 cuboctahedra that share corners with six equivalent Mg(3)Mg10Fe2 cuboctahedra; edges with four equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with eight Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra; and faces with six equivalent Sb(1)Mg10Fe2 cuboctahedra. Both Mg(3)-Mg(4) bond lengths are 3.05 Å. Both Mg(3)-Mg(2,2) bond lengths are 2.89 Å. Both Mg(3)-Fe(1) bond lengths are 2.95 Å. In the sixth Mg site, Mg(4) is bonded in a distorted water-like geometry to two equivalent Mg(3); four Mg(1,1); four Mg(2,2,2,2); and two equivalent Sb(1) atoms. Both Mg(4)-Mg(1) bond lengths are 2.99 Å. Both Mg(4)-Mg(2,2) bond lengths are 2.97 Å. Both Mg(4)-Sb(1) bond lengths are 3.01 Å. In the seventh Mg site, Mg(1) is bonded 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 to form distorted MgMg8Fe2Sb2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Sb2 cuboctahedra. There is one shorter (3.02 Å) and one longer (3.07 Å) Mg(1)-Mg(1) bond length. Both Mg(1)-Mg(2) bond lengths are 3.01 Å. Both Mg(1)-Mg(3) bond lengths are 3.01 Å. There is one shorter (3.04 Å) and one longer (3.05 Å) Mg(1)-Fe(1) bond length. There is one shorter (3.04 Å) and one longer (3.05 Å) Mg(1)-Sb(1) bond length. In the eighth Mg site, Mg(2) 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. Both Mg(2)-Mg(1) bond lengths are 3.01 Å. There is one shorter (2.83 Å) and one longer (3.26 Å) Mg(2)-Mg(2) bond length. Both Mg(2)-Fe(1) bond lengths are 2.93 Å. Both Mg(2)-Sb(1) bond lengths are 3.05 Å. In the ninth Mg site, Mg(2) 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. Both Mg(2)-Fe(1) bond lengths are 2.93 Å. Both Mg(2)-Sb(1) bond lengths are 3.05 Å. Fe(1) is bonded to two equivalent Mg(3); four Mg(1,1,1); four Mg(2,2); and two equivalent Sb(1) atoms to form FeMg10Sb2 cuboctahedra that share corners with four equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with six equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with eight Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Sb(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(3)Mg10Fe2 cuboctahedra; edges with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; faces with two equivalent Mg(3)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra. Both Fe(1)-Sb(1) bond lengths are 3.05 Å. Sb(1) is bonded to two equivalent Mg(4); four Mg(1,1,1); four Mg(2,2); and two equivalent Fe(1) atoms to form SbMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Sb2 cuboctahedra; corners with six equivalent Sb(1)Mg10Fe2 cuboctahedra; corners with eight Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; edges with two equivalent Fe(1)Mg10Sb2 cuboctahedra; edges with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; faces with two equivalent Fe(1)Mg10Sb2 cuboctahedra; faces with two equivalent Sb(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1,1)Mg8Fe2Sb2 cuboctahedra; and faces with six equivalent Mg(3)Mg10Fe2 cuboctahedra.