Mg6HfMo crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 1-coordinate geometry to two equivalent Mg(3), two equivalent Mg(4), and two equivalent Mo(1) atoms. 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 Mo(1) atoms. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Hf(1), and two equivalent Mo(1) atoms to form distorted MgHf2Mg8Mo2 cuboctahedra that share corners with four equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with ten equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, edges with two equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with two equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, and faces with four equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra. 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 Hf(1) atoms to form MgHf2Mg10 cuboctahedra that share corners with six equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with eight equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, edges with four equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, and faces with four equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra. Hf(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Mg(4), four equivalent Mg(3), and two equivalent Mo(1) atoms. Mo(1) is bonded in a 12-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Hf(1) atoms.
Mg6HfMo crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 1-coordinate geometry to two equivalent Mg(3), two equivalent Mg(4), and two equivalent Mo(1) atoms. Both Mg(1)-Mg(3) bond lengths are 2.95 Å. Both Mg(1)-Mg(4) bond lengths are 3.09 Å. There is one shorter (2.94 Å) and one longer (3.41 Å) Mg(1)-Mo(1) bond length. 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 Mo(1) atoms. Both Mg(2)-Mg(4) bond lengths are 3.02 Å. All Mg(2)-Mg(3) bond lengths are 3.12 Å. Both Mg(2)-Mo(1) bond lengths are 3.07 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Hf(1), and two equivalent Mo(1) atoms to form distorted MgHf2Mg8Mo2 cuboctahedra that share corners with four equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with ten equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, edges with two equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with two equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, and faces with four equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra. There is one shorter (2.97 Å) and one longer (3.14 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.07 Å) and one longer (3.28 Å) Mg(3)-Mg(4) bond length. There is one shorter (2.96 Å) and one longer (3.39 Å) Mg(3)-Hf(1) bond length. Both Mg(3)-Mo(1) bond lengths are 3.19 Å. 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 Hf(1) atoms to form MgHf2Mg10 cuboctahedra that share corners with six equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with eight equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, edges with four equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, and faces with four equivalent Mg(3)Hf2Mg8Mo2 cuboctahedra. Both Mg(4)-Hf(1) bond lengths are 3.07 Å. Hf(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Mg(4), four equivalent Mg(3), and two equivalent Mo(1) atoms. Both Hf(1)-Mo(1) bond lengths are 2.71 Å. Mo(1) is bonded in a 12-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Hf(1) atoms.