SrMg6Hf crystallizes in the orthorhombic Cmmm space group. Sr(1) is bonded to four equivalent Mg(1), four equivalent Mg(2), and four equivalent Mg(3) atoms to form SrMg12 cuboctahedra that share corners with four equivalent Sr(1)Mg12 cuboctahedra, corners with eight equivalent Hf(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, faces with two equivalent Sr(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, and faces with four equivalent Hf(1)Mg12 cuboctahedra. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Sr(1), four equivalent Mg(2), four equivalent Mg(3), and two equivalent Hf(1) atoms to form distorted MgSr2Hf2Mg8 cuboctahedra that share corners with twelve equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, edges with four equivalent Sr(1)Mg12 cuboctahedra, edges with four equivalent Hf(1)Mg12 cuboctahedra, faces with two equivalent Sr(1)Mg12 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, and faces with six equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Sr(1), two equivalent Mg(3), four equivalent Mg(1), and two equivalent Hf(1) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to two equivalent Sr(1), two equivalent Mg(2), four equivalent Mg(1), and two equivalent Hf(1) atoms. Hf(1) is bonded to four equivalent Mg(1), four equivalent Mg(2), and four equivalent Mg(3) atoms to form HfMg12 cuboctahedra that share corners with four equivalent Hf(1)Mg12 cuboctahedra, corners with eight equivalent Sr(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, faces with four equivalent Sr(1)Mg12 cuboctahedra, and faces with four equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra.
SrMg6Hf crystallizes in the orthorhombic Cmmm space group. Sr(1) is bonded to four equivalent Mg(1), four equivalent Mg(2), and four equivalent Mg(3) atoms to form SrMg12 cuboctahedra that share corners with four equivalent Sr(1)Mg12 cuboctahedra, corners with eight equivalent Hf(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, faces with two equivalent Sr(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, and faces with four equivalent Hf(1)Mg12 cuboctahedra. All Sr(1)-Mg(1) bond lengths are 3.29 Å. All Sr(1)-Mg(2) bond lengths are 3.42 Å. All Sr(1)-Mg(3) bond lengths are 3.47 Å. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Sr(1), four equivalent Mg(2), four equivalent Mg(3), and two equivalent Hf(1) atoms to form distorted MgSr2Hf2Mg8 cuboctahedra that share corners with twelve equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, edges with four equivalent Sr(1)Mg12 cuboctahedra, edges with four equivalent Hf(1)Mg12 cuboctahedra, faces with two equivalent Sr(1)Mg12 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, and faces with six equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra. All Mg(1)-Mg(2) bond lengths are 3.36 Å. All Mg(1)-Mg(3) bond lengths are 3.27 Å. Both Mg(1)-Hf(1) bond lengths are 3.29 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Sr(1), two equivalent Mg(3), four equivalent Mg(1), and two equivalent Hf(1) atoms. Both Mg(2)-Mg(3) bond lengths are 3.04 Å. Both Mg(2)-Hf(1) bond lengths are 3.13 Å. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to two equivalent Sr(1), two equivalent Mg(2), four equivalent Mg(1), and two equivalent Hf(1) atoms. Both Mg(3)-Hf(1) bond lengths are 3.25 Å. Hf(1) is bonded to four equivalent Mg(1), four equivalent Mg(2), and four equivalent Mg(3) atoms to form HfMg12 cuboctahedra that share corners with four equivalent Hf(1)Mg12 cuboctahedra, corners with eight equivalent Sr(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, faces with four equivalent Sr(1)Mg12 cuboctahedra, and faces with four equivalent Mg(1)Sr2Hf2Mg8 cuboctahedra.