PmY crystallizes in the hexagonal P-6m2 space group. Pm(1) is bonded to six equivalent Pm(1) and six equivalent Y(1) atoms to form PmPm6Y6 cuboctahedra that share corners with eighteen equivalent Pm(1)Pm6Y6 cuboctahedra, edges with six equivalent Pm(1)Pm6Y6 cuboctahedra, edges with twelve equivalent Y(1)Pm6Y6 cuboctahedra, faces with eight equivalent Pm(1)Pm6Y6 cuboctahedra, and faces with twelve equivalent Y(1)Pm6Y6 cuboctahedra. Y(1) is bonded to six equivalent Pm(1) and six equivalent Y(1) atoms to form YPm6Y6 cuboctahedra that share corners with eighteen equivalent Y(1)Pm6Y6 cuboctahedra, edges with six equivalent Y(1)Pm6Y6 cuboctahedra, edges with twelve equivalent Pm(1)Pm6Y6 cuboctahedra, faces with eight equivalent Y(1)Pm6Y6 cuboctahedra, and faces with twelve equivalent Pm(1)Pm6Y6 cuboctahedra.
PmY crystallizes in the hexagonal P-6m2 space group. Pm(1) is bonded to six equivalent Pm(1) and six equivalent Y(1) atoms to form PmPm6Y6 cuboctahedra that share corners with eighteen equivalent Pm(1)Pm6Y6 cuboctahedra, edges with six equivalent Pm(1)Pm6Y6 cuboctahedra, edges with twelve equivalent Y(1)Pm6Y6 cuboctahedra, faces with eight equivalent Pm(1)Pm6Y6 cuboctahedra, and faces with twelve equivalent Y(1)Pm6Y6 cuboctahedra. All Pm(1)-Pm(1) bond lengths are 3.69 Å. All Pm(1)-Y(1) bond lengths are 3.65 Å. Y(1) is bonded to six equivalent Pm(1) and six equivalent Y(1) atoms to form YPm6Y6 cuboctahedra that share corners with eighteen equivalent Y(1)Pm6Y6 cuboctahedra, edges with six equivalent Y(1)Pm6Y6 cuboctahedra, edges with twelve equivalent Pm(1)Pm6Y6 cuboctahedra, faces with eight equivalent Y(1)Pm6Y6 cuboctahedra, and faces with twelve equivalent Pm(1)Pm6Y6 cuboctahedra. All Y(1)-Y(1) bond lengths are 3.69 Å.