Nb3Co8Al is Hexagonal Laves-derived structured and crystallizes in the trigonal R3m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(3), three equivalent Nb(2), three equivalent Co(1), three equivalent Co(4), and six equivalent Co(2) atoms. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to three equivalent Nb(1), three equivalent Co(2), three equivalent Co(4), six equivalent Co(1), and one Al(1) atom. In the third Nb site, Nb(3) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Co(1), three equivalent Co(3), six equivalent Co(2), and three equivalent Al(1) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one Nb(1), one Nb(3), two equivalent Nb(2), one Co(3), one Co(4), four equivalent Co(1), and two equivalent Al(1) atoms to form CoNb4Al2Co6 cuboctahedra that share corners with two equivalent Co(3)Nb3Al3Co6 cuboctahedra, corners with two equivalent Co(4)Nb6Co6 cuboctahedra, corners with four equivalent Co(1)Nb4Al2Co6 cuboctahedra, corners with ten equivalent Co(2)Nb5AlCo6 cuboctahedra, edges with two equivalent Co(1)Nb4Al2Co6 cuboctahedra, edges with four equivalent Co(2)Nb5AlCo6 cuboctahedra, faces with three equivalent Co(3)Nb3Al3Co6 cuboctahedra, faces with three equivalent Co(4)Nb6Co6 cuboctahedra, faces with four equivalent Co(2)Nb5AlCo6 cuboctahedra, and faces with eight equivalent Co(1)Nb4Al2Co6 cuboctahedra. In the second Co site, Co(2) is bonded to one Nb(2), two equivalent Nb(1), two equivalent Nb(3), one Co(3), one Co(4), four equivalent Co(2), and one Al(1) atom to form CoNb5AlCo6 cuboctahedra that share corners with two equivalent Co(3)Nb3Al3Co6 cuboctahedra, corners with two equivalent Co(4)Nb6Co6 cuboctahedra, corners with four equivalent Co(2)Nb5AlCo6 cuboctahedra, corners with ten equivalent Co(1)Nb4Al2Co6 cuboctahedra, edges with two equivalent Co(2)Nb5AlCo6 cuboctahedra, edges with four equivalent Co(1)Nb4Al2Co6 cuboctahedra, faces with three equivalent Co(3)Nb3Al3Co6 cuboctahedra, faces with three equivalent Co(4)Nb6Co6 cuboctahedra, faces with four equivalent Co(1)Nb4Al2Co6 cuboctahedra, and faces with eight equivalent Co(2)Nb5AlCo6 cuboctahedra. In the third Co site, Co(3) is bonded to three equivalent Nb(3), three equivalent Co(1), three equivalent Co(2), and three equivalent Al(1) atoms to form CoNb3Al3Co6 cuboctahedra that share corners with six equivalent Co(1)Nb4Al2Co6 cuboctahedra, corners with six equivalent Co(2)Nb5AlCo6 cuboctahedra, corners with six equivalent Co(4)Nb6Co6 cuboctahedra, edges with six equivalent Co(3)Nb3Al3Co6 cuboctahedra, faces with nine equivalent Co(1)Nb4Al2Co6 cuboctahedra, and faces with nine equivalent Co(2)Nb5AlCo6 cuboctahedra. In the fourth Co site, Co(4) is bonded to three equivalent Nb(1), three equivalent Nb(2), three equivalent Co(1), and three equivalent Co(2) atoms to form CoNb6Co6 cuboctahedra that share corners with six equivalent Co(3)Nb3Al3Co6 cuboctahedra, corners with six equivalent Co(1)Nb4Al2Co6 cuboctahedra, corners with six equivalent Co(2)Nb5AlCo6 cuboctahedra, edges with six equivalent Co(4)Nb6Co6 cuboctahedra, faces with nine equivalent Co(1)Nb4Al2Co6 cuboctahedra, and faces with nine equivalent Co(2)Nb5AlCo6 cuboctahedra. Al(1) is bonded in a 16-coordinate geometry to one Nb(2), three equivalent Nb(3), three equivalent Co(2), three equivalent Co(3), and six equivalent Co(1) atoms.
Nb3Co8Al is Hexagonal Laves-derived structured and crystallizes in the trigonal R3m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(3), three equivalent Nb(2), three equivalent Co(1), three equivalent Co(4), and six equivalent Co(2) atoms. The Nb(1)-Nb(3) bond length is 2.90 Å. All Nb(1)-Nb(2) bond lengths are 2.95 Å. All Nb(1)-Co(1) bond lengths are 2.82 Å. All Nb(1)-Co(4) bond lengths are 2.79 Å. All Nb(1)-Co(2) bond lengths are 2.75 Å. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to three equivalent Nb(1), three equivalent Co(2), three equivalent Co(4), six equivalent Co(1), and one Al(1) atom. All Nb(2)-Co(2) bond lengths are 2.85 Å. All Nb(2)-Co(4) bond lengths are 2.80 Å. All Nb(2)-Co(1) bond lengths are 2.74 Å. The Nb(2)-Al(1) bond length is 2.85 Å. In the third Nb site, Nb(3) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Co(1), three equivalent Co(3), six equivalent Co(2), and three equivalent Al(1) atoms. All Nb(3)-Co(1) bond lengths are 2.74 Å. All Nb(3)-Co(3) bond lengths are 2.78 Å. All Nb(3)-Co(2) bond lengths are 2.81 Å. All Nb(3)-Al(1) bond lengths are 2.88 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one Nb(1), one Nb(3), two equivalent Nb(2), one Co(3), one Co(4), four equivalent Co(1), and two equivalent Al(1) atoms to form CoNb4Al2Co6 cuboctahedra that share corners with two equivalent Co(3)Nb3Al3Co6 cuboctahedra, corners with two equivalent Co(4)Nb6Co6 cuboctahedra, corners with four equivalent Co(1)Nb4Al2Co6 cuboctahedra, corners with ten equivalent Co(2)Nb5AlCo6 cuboctahedra, edges with two equivalent Co(1)Nb4Al2Co6 cuboctahedra, edges with four equivalent Co(2)Nb5AlCo6 cuboctahedra, faces with three equivalent Co(3)Nb3Al3Co6 cuboctahedra, faces with three equivalent Co(4)Nb6Co6 cuboctahedra, faces with four equivalent Co(2)Nb5AlCo6 cuboctahedra, and faces with eight equivalent Co(1)Nb4Al2Co6 cuboctahedra. The Co(1)-Co(3) bond length is 2.35 Å. The Co(1)-Co(4) bond length is 2.38 Å. There are two shorter (2.35 Å) and two longer (2.39 Å) Co(1)-Co(1) bond lengths. Both Co(1)-Al(1) bond lengths are 2.79 Å. In the second Co site, Co(2) is bonded to one Nb(2), two equivalent Nb(1), two equivalent Nb(3), one Co(3), one Co(4), four equivalent Co(2), and one Al(1) atom to form CoNb5AlCo6 cuboctahedra that share corners with two equivalent Co(3)Nb3Al3Co6 cuboctahedra, corners with two equivalent Co(4)Nb6Co6 cuboctahedra, corners with four equivalent Co(2)Nb5AlCo6 cuboctahedra, corners with ten equivalent Co(1)Nb4Al2Co6 cuboctahedra, edges with two equivalent Co(2)Nb5AlCo6 cuboctahedra, edges with four equivalent Co(1)Nb4Al2Co6 cuboctahedra, faces with three equivalent Co(3)Nb3Al3Co6 cuboctahedra, faces with three equivalent Co(4)Nb6Co6 cuboctahedra, faces with four equivalent Co(1)Nb4Al2Co6 cuboctahedra, and faces with eight equivalent Co(2)Nb5AlCo6 cuboctahedra. The Co(2)-Co(3) bond length is 2.40 Å. The Co(2)-Co(4) bond length is 2.36 Å. There are two shorter (2.36 Å) and two longer (2.39 Å) Co(2)-Co(2) bond lengths. The Co(2)-Al(1) bond length is 2.76 Å. In the third Co site, Co(3) is bonded to three equivalent Nb(3), three equivalent Co(1), three equivalent Co(2), and three equivalent Al(1) atoms to form CoNb3Al3Co6 cuboctahedra that share corners with six equivalent Co(1)Nb4Al2Co6 cuboctahedra, corners with six equivalent Co(2)Nb5AlCo6 cuboctahedra, corners with six equivalent Co(4)Nb6Co6 cuboctahedra, edges with six equivalent Co(3)Nb3Al3Co6 cuboctahedra, faces with nine equivalent Co(1)Nb4Al2Co6 cuboctahedra, and faces with nine equivalent Co(2)Nb5AlCo6 cuboctahedra. All Co(3)-Al(1) bond lengths are 2.77 Å. In the fourth Co site, Co(4) is bonded to three equivalent Nb(1), three equivalent Nb(2), three equivalent Co(1), and three equivalent Co(2) atoms to form CoNb6Co6 cuboctahedra that share corners with six equivalent Co(3)Nb3Al3Co6 cuboctahedra, corners with six equivalent Co(1)Nb4Al2Co6 cuboctahedra, corners with six equivalent Co(2)Nb5AlCo6 cuboctahedra, edges with six equivalent Co(4)Nb6Co6 cuboctahedra, faces with nine equivalent Co(1)Nb4Al2Co6 cuboctahedra, and faces with nine equivalent Co(2)Nb5AlCo6 cuboctahedra. Al(1) is bonded in a 16-coordinate geometry to one Nb(2), three equivalent Nb(3), three equivalent Co(2), three equivalent Co(3), and six equivalent Co(1) atoms.