Co7Hf crystallizes in the orthorhombic Cmmm space group. Hf(1) is bonded to four equivalent Co(2), four equivalent Co(3), and four equivalent Co(4) atoms to form HfCo12 cuboctahedra that share corners with four equivalent Hf(1)Co12 cuboctahedra, corners with eight equivalent Co(1)Co12 cuboctahedra, edges with eight equivalent Co(3)Hf2Co10 cuboctahedra, edges with eight equivalent Co(4)Hf2Co10 cuboctahedra, faces with two equivalent Hf(1)Co12 cuboctahedra, faces with four equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Co(3)Hf2Co10 cuboctahedra, and faces with four equivalent Co(4)Hf2Co10 cuboctahedra. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to four equivalent Co(2), four equivalent Co(3), and four equivalent Co(4) atoms to form CoCo12 cuboctahedra that share corners with four equivalent Co(1)Co12 cuboctahedra, corners with eight equivalent Hf(1)Co12 cuboctahedra, edges with eight equivalent Co(3)Hf2Co10 cuboctahedra, edges with eight equivalent Co(4)Hf2Co10 cuboctahedra, faces with two equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Hf(1)Co12 cuboctahedra, faces with four equivalent Co(3)Hf2Co10 cuboctahedra, and faces with four equivalent Co(4)Hf2Co10 cuboctahedra. In the second Co site, Co(2) is bonded in a 12-coordinate geometry to two equivalent Hf(1), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms. In the third Co site, Co(3) is bonded to two equivalent Hf(1), two equivalent Co(1), four equivalent Co(2), and four equivalent Co(4) atoms to form distorted CoHf2Co10 cuboctahedra that share corners with twelve equivalent Co(3)Hf2Co10 cuboctahedra, edges with four equivalent Hf(1)Co12 cuboctahedra, edges with four equivalent Co(1)Co12 cuboctahedra, edges with eight equivalent Co(4)Hf2Co10 cuboctahedra, faces with two equivalent Hf(1)Co12 cuboctahedra, faces with two equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Co(4)Hf2Co10 cuboctahedra, and faces with six equivalent Co(3)Hf2Co10 cuboctahedra. In the fourth Co site, Co(4) is bonded to two equivalent Hf(1), two equivalent Co(1), four equivalent Co(2), and four equivalent Co(3) atoms to form distorted CoHf2Co10 cuboctahedra that share corners with twelve equivalent Co(4)Hf2Co10 cuboctahedra, edges with four equivalent Hf(1)Co12 cuboctahedra, edges with four equivalent Co(1)Co12 cuboctahedra, edges with eight equivalent Co(3)Hf2Co10 cuboctahedra, faces with two equivalent Hf(1)Co12 cuboctahedra, faces with two equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Co(3)Hf2Co10 cuboctahedra, and faces with six equivalent Co(4)Hf2Co10 cuboctahedra.
Co7Hf crystallizes in the orthorhombic Cmmm space group. Hf(1) is bonded to four equivalent Co(2), four equivalent Co(3), and four equivalent Co(4) atoms to form HfCo12 cuboctahedra that share corners with four equivalent Hf(1)Co12 cuboctahedra, corners with eight equivalent Co(1)Co12 cuboctahedra, edges with eight equivalent Co(3)Hf2Co10 cuboctahedra, edges with eight equivalent Co(4)Hf2Co10 cuboctahedra, faces with two equivalent Hf(1)Co12 cuboctahedra, faces with four equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Co(3)Hf2Co10 cuboctahedra, and faces with four equivalent Co(4)Hf2Co10 cuboctahedra. All Hf(1)-Co(2) bond lengths are 2.64 Å. All Hf(1)-Co(3) bond lengths are 2.66 Å. All Hf(1)-Co(4) bond lengths are 2.60 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to four equivalent Co(2), four equivalent Co(3), and four equivalent Co(4) atoms to form CoCo12 cuboctahedra that share corners with four equivalent Co(1)Co12 cuboctahedra, corners with eight equivalent Hf(1)Co12 cuboctahedra, edges with eight equivalent Co(3)Hf2Co10 cuboctahedra, edges with eight equivalent Co(4)Hf2Co10 cuboctahedra, faces with two equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Hf(1)Co12 cuboctahedra, faces with four equivalent Co(3)Hf2Co10 cuboctahedra, and faces with four equivalent Co(4)Hf2Co10 cuboctahedra. All Co(1)-Co(2) bond lengths are 2.46 Å. All Co(1)-Co(3) bond lengths are 2.47 Å. All Co(1)-Co(4) bond lengths are 2.60 Å. In the second Co site, Co(2) is bonded in a 12-coordinate geometry to two equivalent Hf(1), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms. There are two shorter (2.41 Å) and two longer (2.78 Å) Co(2)-Co(3) bond lengths. All Co(2)-Co(4) bond lengths are 2.57 Å. In the third Co site, Co(3) is bonded to two equivalent Hf(1), two equivalent Co(1), four equivalent Co(2), and four equivalent Co(4) atoms to form distorted CoHf2Co10 cuboctahedra that share corners with twelve equivalent Co(3)Hf2Co10 cuboctahedra, edges with four equivalent Hf(1)Co12 cuboctahedra, edges with four equivalent Co(1)Co12 cuboctahedra, edges with eight equivalent Co(4)Hf2Co10 cuboctahedra, faces with two equivalent Hf(1)Co12 cuboctahedra, faces with two equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Co(4)Hf2Co10 cuboctahedra, and faces with six equivalent Co(3)Hf2Co10 cuboctahedra. All Co(3)-Co(4) bond lengths are 2.56 Å. In the fourth Co site, Co(4) is bonded to two equivalent Hf(1), two equivalent Co(1), four equivalent Co(2), and four equivalent Co(3) atoms to form distorted CoHf2Co10 cuboctahedra that share corners with twelve equivalent Co(4)Hf2Co10 cuboctahedra, edges with four equivalent Hf(1)Co12 cuboctahedra, edges with four equivalent Co(1)Co12 cuboctahedra, edges with eight equivalent Co(3)Hf2Co10 cuboctahedra, faces with two equivalent Hf(1)Co12 cuboctahedra, faces with two equivalent Co(1)Co12 cuboctahedra, faces with four equivalent Co(3)Hf2Co10 cuboctahedra, and faces with six equivalent Co(4)Hf2Co10 cuboctahedra.