Mg6NbFe crystallizes in the orthorhombic Amm2 space group. There are four 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 Nb(1), and two equivalent Fe(1) atoms to form distorted MgMg8Nb2Fe2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Fe2 cuboctahedra, corners with four equivalent Fe(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Nb(1)Mg10Fe2 cuboctahedra, edges with two equivalent Fe(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra. In the second 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 Nb(1), and two equivalent Fe(1) atoms. In the third Mg site, Mg(3) is bonded in a distorted bent 120 degrees geometry to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Fe(1) atoms. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with six equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Nb(1)Mg10Fe2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, and faces with six equivalent Fe(1)Mg10Nb2 cuboctahedra. Nb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Fe(1) atoms to form NbMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Fe2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Fe(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra. Fe(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form FeMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Fe2 cuboctahedra, corners with six equivalent Fe(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Nb(1)Mg10Fe2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Nb2 cuboctahedra.
Mg6NbFe crystallizes in the orthorhombic Amm2 space group. There are four 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 Nb(1), and two equivalent Fe(1) atoms to form distorted MgMg8Nb2Fe2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Fe2 cuboctahedra, corners with four equivalent Fe(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Nb(1)Mg10Fe2 cuboctahedra, edges with two equivalent Fe(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra. There is one shorter (2.85 Å) and one longer (2.87 Å) Mg(1)-Mg(1) bond length. Both Mg(1)-Mg(2) bond lengths are 2.97 Å. Both Mg(1)-Mg(3) bond lengths are 3.09 Å. Both Mg(1)-Mg(4) bond lengths are 3.01 Å. There is one shorter (3.05 Å) and one longer (3.11 Å) Mg(1)-Nb(1) bond length. There is one shorter (2.99 Å) and one longer (3.17 Å) Mg(1)-Fe(1) bond length. In the second 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 Nb(1), and two equivalent Fe(1) atoms. There is one shorter (2.85 Å) and one longer (2.88 Å) Mg(2)-Mg(2) bond length. There is one shorter (2.82 Å) and one longer (3.35 Å) Mg(2)-Mg(3) bond length. There is one shorter (3.00 Å) and one longer (3.16 Å) Mg(2)-Mg(4) bond length. Both Mg(2)-Nb(1) bond lengths are 2.99 Å. Both Mg(2)-Fe(1) bond lengths are 2.94 Å. In the third Mg site, Mg(3) is bonded in a distorted bent 120 degrees geometry to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Fe(1) atoms. Both Mg(3)-Mg(4) bond lengths are 2.87 Å. Both Mg(3)-Fe(1) bond lengths are 2.86 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with six equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Nb(1)Mg10Fe2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, and faces with six equivalent Fe(1)Mg10Nb2 cuboctahedra. Both Mg(4)-Nb(1) bond lengths are 2.90 Å. Nb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Fe(1) atoms to form NbMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Fe2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Fe(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra. Both Nb(1)-Fe(1) bond lengths are 2.87 Å. Fe(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form FeMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Fe2 cuboctahedra, corners with six equivalent Fe(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, edges with two equivalent Nb(1)Mg10Fe2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, faces with two equivalent Nb(1)Mg10Fe2 cuboctahedra, faces with two equivalent Fe(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Fe2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Nb2 cuboctahedra.