Rb3Hf is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to four equivalent Rb(1), four equivalent Rb(2), and four equivalent Hf(1) atoms to form distorted RbRb8Hf4 cuboctahedra that share corners with twelve equivalent Rb(1)Rb8Hf4 cuboctahedra, edges with eight equivalent Rb(1)Rb8Hf4 cuboctahedra, edges with eight equivalent Rb(2)Rb8Hf4 cuboctahedra, edges with eight equivalent Hf(1)Rb12 cuboctahedra, faces with four equivalent Rb(2)Rb8Hf4 cuboctahedra, faces with four equivalent Hf(1)Rb12 cuboctahedra, and faces with ten equivalent Rb(1)Rb8Hf4 cuboctahedra. In the second Rb site, Rb(2) is bonded to eight equivalent Rb(1) and four equivalent Hf(1) atoms to form RbRb8Hf4 cuboctahedra that share corners with four equivalent Rb(2)Rb8Hf4 cuboctahedra, corners with eight equivalent Hf(1)Rb12 cuboctahedra, edges with eight equivalent Rb(2)Rb8Hf4 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Hf4 cuboctahedra, faces with four equivalent Rb(2)Rb8Hf4 cuboctahedra, faces with six equivalent Hf(1)Rb12 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Hf4 cuboctahedra. Hf(1) is bonded to four equivalent Rb(2) and eight equivalent Rb(1) atoms to form HfRb12 cuboctahedra that share corners with four equivalent Hf(1)Rb12 cuboctahedra, corners with eight equivalent Rb(2)Rb8Hf4 cuboctahedra, edges with eight equivalent Hf(1)Rb12 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Hf4 cuboctahedra, faces with four equivalent Hf(1)Rb12 cuboctahedra, faces with six equivalent Rb(2)Rb8Hf4 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Hf4 cuboctahedra.
Rb3Hf is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to four equivalent Rb(1), four equivalent Rb(2), and four equivalent Hf(1) atoms to form distorted RbRb8Hf4 cuboctahedra that share corners with twelve equivalent Rb(1)Rb8Hf4 cuboctahedra, edges with eight equivalent Rb(1)Rb8Hf4 cuboctahedra, edges with eight equivalent Rb(2)Rb8Hf4 cuboctahedra, edges with eight equivalent Hf(1)Rb12 cuboctahedra, faces with four equivalent Rb(2)Rb8Hf4 cuboctahedra, faces with four equivalent Hf(1)Rb12 cuboctahedra, and faces with ten equivalent Rb(1)Rb8Hf4 cuboctahedra. All Rb(1)-Rb(1) bond lengths are 4.39 Å. All Rb(1)-Rb(2) bond lengths are 4.35 Å. All Rb(1)-Hf(1) bond lengths are 4.35 Å. In the second Rb site, Rb(2) is bonded to eight equivalent Rb(1) and four equivalent Hf(1) atoms to form RbRb8Hf4 cuboctahedra that share corners with four equivalent Rb(2)Rb8Hf4 cuboctahedra, corners with eight equivalent Hf(1)Rb12 cuboctahedra, edges with eight equivalent Rb(2)Rb8Hf4 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Hf4 cuboctahedra, faces with four equivalent Rb(2)Rb8Hf4 cuboctahedra, faces with six equivalent Hf(1)Rb12 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Hf4 cuboctahedra. All Rb(2)-Hf(1) bond lengths are 4.39 Å. Hf(1) is bonded to four equivalent Rb(2) and eight equivalent Rb(1) atoms to form HfRb12 cuboctahedra that share corners with four equivalent Hf(1)Rb12 cuboctahedra, corners with eight equivalent Rb(2)Rb8Hf4 cuboctahedra, edges with eight equivalent Hf(1)Rb12 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Hf4 cuboctahedra, faces with four equivalent Hf(1)Rb12 cuboctahedra, faces with six equivalent Rb(2)Rb8Hf4 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Hf4 cuboctahedra.