RbMg6Hf crystallizes in the orthorhombic Amm2 space group. Rb(1) is bonded to two equivalent Mg(3), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(2) atoms to form RbMg12 cuboctahedra that share corners with four equivalent Rb(1)Mg12 cuboctahedra, corners with eight equivalent Hf(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, faces with two equivalent Rb(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, and faces with four equivalent Hf(1)Mg12 cuboctahedra. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Rb(1), two equivalent Mg(3), two equivalent Mg(4), four equivalent Mg(2), and two equivalent Hf(1) atoms to form distorted MgRb2Hf2Mg8 cuboctahedra that share corners with twelve equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, edges with four equivalent Rb(1)Mg12 cuboctahedra, edges with four equivalent Hf(1)Mg12 cuboctahedra, faces with two equivalent Rb(1)Mg12 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, and faces with six equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Rb(1), one Mg(3), one Mg(4), 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 Rb(1), two equivalent Mg(2), four equivalent Mg(1), and two equivalent Hf(1) atoms. In the fourth Mg site, Mg(4) is bonded in a 10-coordinate geometry to two equivalent Rb(1), two equivalent Mg(2), four equivalent Mg(1), and two equivalent Hf(1) atoms. Hf(1) is bonded to two equivalent Mg(3), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(2) atoms to form HfMg12 cuboctahedra that share corners with four equivalent Hf(1)Mg12 cuboctahedra, corners with eight equivalent Rb(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, faces with four equivalent Rb(1)Mg12 cuboctahedra, and faces with four equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra.
RbMg6Hf crystallizes in the orthorhombic Amm2 space group. Rb(1) is bonded to two equivalent Mg(3), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(2) atoms to form RbMg12 cuboctahedra that share corners with four equivalent Rb(1)Mg12 cuboctahedra, corners with eight equivalent Hf(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, faces with two equivalent Rb(1)Mg12 cuboctahedra, faces with four equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, and faces with four equivalent Hf(1)Mg12 cuboctahedra. Both Rb(1)-Mg(3) bond lengths are 3.53 Å. Both Rb(1)-Mg(4) bond lengths are 3.61 Å. There are two shorter (3.41 Å) and two longer (3.44 Å) Rb(1)-Mg(1) bond lengths. All Rb(1)-Mg(2) bond lengths are 3.57 Å. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Rb(1), two equivalent Mg(3), two equivalent Mg(4), four equivalent Mg(2), and two equivalent Hf(1) atoms to form distorted MgRb2Hf2Mg8 cuboctahedra that share corners with twelve equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, edges with four equivalent Rb(1)Mg12 cuboctahedra, edges with four equivalent Hf(1)Mg12 cuboctahedra, faces with two equivalent Rb(1)Mg12 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, and faces with six equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra. Both Mg(1)-Mg(3) bond lengths are 3.40 Å. Both Mg(1)-Mg(4) bond lengths are 3.32 Å. There are two shorter (3.33 Å) and two longer (3.37 Å) Mg(1)-Mg(2) bond lengths. There is one shorter (3.39 Å) and one longer (3.46 Å) Mg(1)-Hf(1) bond length. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Rb(1), one Mg(3), one Mg(4), four equivalent Mg(1), and two equivalent Hf(1) atoms. The Mg(2)-Mg(3) bond length is 2.97 Å. The Mg(2)-Mg(4) bond length is 3.00 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 Rb(1), two equivalent Mg(2), four equivalent Mg(1), and two equivalent Hf(1) atoms. Both Mg(3)-Hf(1) bond lengths are 3.12 Å. In the fourth Mg site, Mg(4) is bonded in a 10-coordinate geometry to two equivalent Rb(1), two equivalent Mg(2), four equivalent Mg(1), and two equivalent Hf(1) atoms. Both Mg(4)-Hf(1) bond lengths are 3.12 Å. Hf(1) is bonded to two equivalent Mg(3), two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(2) atoms to form HfMg12 cuboctahedra that share corners with four equivalent Hf(1)Mg12 cuboctahedra, corners with eight equivalent Rb(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra, faces with two equivalent Hf(1)Mg12 cuboctahedra, faces with four equivalent Rb(1)Mg12 cuboctahedra, and faces with four equivalent Mg(1)Rb2Hf2Mg8 cuboctahedra.