Mg6NbMo 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 Mo(1) atoms to form distorted MgMg8Nb2Mo2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Mo2 cuboctahedra, corners with four equivalent Mo(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Nb(1)Mg10Mo2 cuboctahedra, edges with two equivalent Mo(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Mo2 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 Mo(1) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Mg(4), 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(3)Mg10Nb2 cuboctahedra, edges with four equivalent Nb(1)Mg10Mo2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, faces with two equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, and faces with six equivalent Mo(1)Mg10Nb2 cuboctahedra. In the fourth Mg site, Mg(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Mo(1) atoms. Nb(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Mo(1) atoms to form NbMg10Mo2 cuboctahedra that share corners with four equivalent Mo(1)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Mo2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Mo(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, faces with two equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra. Mo(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form MoMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Mo2 cuboctahedra, corners with six equivalent Mo(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Nb(1)Mg10Mo2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, and faces with six equivalent Mg(3)Mg10Nb2 cuboctahedra.
Mg6NbMo 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 Mo(1) atoms to form distorted MgMg8Nb2Mo2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Mo2 cuboctahedra, corners with four equivalent Mo(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Nb(1)Mg10Mo2 cuboctahedra, edges with two equivalent Mo(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 2.88 Å. Both Mg(1)-Mg(2) bond lengths are 3.08 Å. Both Mg(1)-Mg(3) bond lengths are 3.09 Å. Both Mg(1)-Mg(4) bond lengths are 3.11 Å. There is one shorter (3.11 Å) and one longer (3.13 Å) Mg(1)-Nb(1) bond length. Both Mg(1)-Mo(1) bond lengths are 3.12 Å. 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 Mo(1) atoms. There is one shorter (2.84 Å) and one longer (2.92 Å) Mg(2)-Mg(2) bond length. There is one shorter (2.97 Å) and one longer (3.27 Å) Mg(2)-Mg(3) bond length. There is one shorter (2.91 Å) and one longer (3.33 Å) Mg(2)-Mg(4) bond length. Both Mg(2)-Nb(1) bond lengths are 3.04 Å. Both Mg(2)-Mo(1) bond lengths are 3.02 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(4), 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(3)Mg10Nb2 cuboctahedra, edges with four equivalent Nb(1)Mg10Mo2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, faces with two equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, and faces with six equivalent Mo(1)Mg10Nb2 cuboctahedra. Both Mg(3)-Mg(4) bond lengths are 2.88 Å. Both Mg(3)-Nb(1) bond lengths are 2.98 Å. In the fourth Mg site, Mg(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Mo(1) atoms. Both Mg(4)-Mo(1) bond lengths are 2.95 Å. Nb(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Mo(1) atoms to form NbMg10Mo2 cuboctahedra that share corners with four equivalent Mo(1)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Mo2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Mo(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, faces with two equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Nb2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra. Both Nb(1)-Mo(1) bond lengths are 2.88 Å. Mo(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form MoMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Mo2 cuboctahedra, corners with six equivalent Mo(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, edges with two equivalent Nb(1)Mg10Mo2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, faces with two equivalent Nb(1)Mg10Mo2 cuboctahedra, faces with two equivalent Mo(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Mo2 cuboctahedra, and faces with six equivalent Mg(3)Mg10Nb2 cuboctahedra.