Rb3Tb 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 Tb(1) atoms to form RbRb8Tb4 cuboctahedra that share corners with twelve equivalent Rb(1)Rb8Tb4 cuboctahedra, edges with eight equivalent Rb(1)Rb8Tb4 cuboctahedra, edges with eight equivalent Rb(2)Rb8Tb4 cuboctahedra, edges with eight equivalent Tb(1)Rb12 cuboctahedra, faces with four equivalent Rb(2)Rb8Tb4 cuboctahedra, faces with four equivalent Tb(1)Rb12 cuboctahedra, and faces with ten equivalent Rb(1)Rb8Tb4 cuboctahedra. In the second Rb site, Rb(2) is bonded to eight equivalent Rb(1) and four equivalent Tb(1) atoms to form distorted RbRb8Tb4 cuboctahedra that share corners with four equivalent Rb(2)Rb8Tb4 cuboctahedra, corners with eight equivalent Tb(1)Rb12 cuboctahedra, edges with eight equivalent Rb(2)Rb8Tb4 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Tb4 cuboctahedra, faces with four equivalent Rb(2)Rb8Tb4 cuboctahedra, faces with six equivalent Tb(1)Rb12 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Tb4 cuboctahedra. Tb(1) is bonded to four equivalent Rb(2) and eight equivalent Rb(1) atoms to form TbRb12 cuboctahedra that share corners with four equivalent Tb(1)Rb12 cuboctahedra, corners with eight equivalent Rb(2)Rb8Tb4 cuboctahedra, edges with eight equivalent Tb(1)Rb12 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Tb4 cuboctahedra, faces with four equivalent Tb(1)Rb12 cuboctahedra, faces with six equivalent Rb(2)Rb8Tb4 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Tb4 cuboctahedra.
Rb3Tb 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 Tb(1) atoms to form RbRb8Tb4 cuboctahedra that share corners with twelve equivalent Rb(1)Rb8Tb4 cuboctahedra, edges with eight equivalent Rb(1)Rb8Tb4 cuboctahedra, edges with eight equivalent Rb(2)Rb8Tb4 cuboctahedra, edges with eight equivalent Tb(1)Rb12 cuboctahedra, faces with four equivalent Rb(2)Rb8Tb4 cuboctahedra, faces with four equivalent Tb(1)Rb12 cuboctahedra, and faces with ten equivalent Rb(1)Rb8Tb4 cuboctahedra. All Rb(1)-Rb(1) bond lengths are 4.41 Å. All Rb(1)-Rb(2) bond lengths are 4.62 Å. All Rb(1)-Tb(1) bond lengths are 4.62 Å. In the second Rb site, Rb(2) is bonded to eight equivalent Rb(1) and four equivalent Tb(1) atoms to form distorted RbRb8Tb4 cuboctahedra that share corners with four equivalent Rb(2)Rb8Tb4 cuboctahedra, corners with eight equivalent Tb(1)Rb12 cuboctahedra, edges with eight equivalent Rb(2)Rb8Tb4 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Tb4 cuboctahedra, faces with four equivalent Rb(2)Rb8Tb4 cuboctahedra, faces with six equivalent Tb(1)Rb12 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Tb4 cuboctahedra. All Rb(2)-Tb(1) bond lengths are 4.41 Å. Tb(1) is bonded to four equivalent Rb(2) and eight equivalent Rb(1) atoms to form TbRb12 cuboctahedra that share corners with four equivalent Tb(1)Rb12 cuboctahedra, corners with eight equivalent Rb(2)Rb8Tb4 cuboctahedra, edges with eight equivalent Tb(1)Rb12 cuboctahedra, edges with sixteen equivalent Rb(1)Rb8Tb4 cuboctahedra, faces with four equivalent Tb(1)Rb12 cuboctahedra, faces with six equivalent Rb(2)Rb8Tb4 cuboctahedra, and faces with eight equivalent Rb(1)Rb8Tb4 cuboctahedra.