Nb3Cr8Al 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 Cr(1), three equivalent Cr(4), and six equivalent Cr(2) atoms. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to three equivalent Nb(1), three equivalent Cr(2), three equivalent Cr(4), six equivalent Cr(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 Cr(1), three equivalent Cr(3), six equivalent Cr(2), and three equivalent Al(1) atoms. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Nb(1), one Nb(3), two equivalent Nb(2), one Cr(3), one Cr(4), four equivalent Cr(1), and two equivalent Al(1) atoms to form CrNb4Al2Cr6 cuboctahedra that share corners with two equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, corners with two equivalent Cr(4)Nb6Cr6 cuboctahedra, corners with four equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, corners with ten equivalent Cr(2)Nb5AlCr6 cuboctahedra, edges with two equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, edges with four equivalent Cr(2)Nb5AlCr6 cuboctahedra, faces with three equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, faces with three equivalent Cr(4)Nb6Cr6 cuboctahedra, faces with four equivalent Cr(2)Nb5AlCr6 cuboctahedra, and faces with eight equivalent Cr(1)Nb4Al2Cr6 cuboctahedra. In the second Cr site, Cr(2) is bonded to one Nb(2), two equivalent Nb(1), two equivalent Nb(3), one Cr(3), one Cr(4), four equivalent Cr(2), and one Al(1) atom to form CrNb5AlCr6 cuboctahedra that share corners with two equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, corners with two equivalent Cr(4)Nb6Cr6 cuboctahedra, corners with four equivalent Cr(2)Nb5AlCr6 cuboctahedra, corners with ten equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, edges with two equivalent Cr(2)Nb5AlCr6 cuboctahedra, edges with four equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, faces with three equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, faces with three equivalent Cr(4)Nb6Cr6 cuboctahedra, faces with four equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, and faces with eight equivalent Cr(2)Nb5AlCr6 cuboctahedra. In the third Cr site, Cr(3) is bonded to three equivalent Nb(3), three equivalent Cr(1), three equivalent Cr(2), and three equivalent Al(1) atoms to form CrNb3Al3Cr6 cuboctahedra that share corners with six equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, corners with six equivalent Cr(2)Nb5AlCr6 cuboctahedra, corners with six equivalent Cr(4)Nb6Cr6 cuboctahedra, edges with six equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, faces with nine equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, and faces with nine equivalent Cr(2)Nb5AlCr6 cuboctahedra. In the fourth Cr site, Cr(4) is bonded to three equivalent Nb(1), three equivalent Nb(2), three equivalent Cr(1), and three equivalent Cr(2) atoms to form CrNb6Cr6 cuboctahedra that share corners with six equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, corners with six equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, corners with six equivalent Cr(2)Nb5AlCr6 cuboctahedra, edges with six equivalent Cr(4)Nb6Cr6 cuboctahedra, faces with nine equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, and faces with nine equivalent Cr(2)Nb5AlCr6 cuboctahedra. Al(1) is bonded in a 16-coordinate geometry to one Nb(2), three equivalent Nb(3), three equivalent Cr(2), three equivalent Cr(3), and six equivalent Cr(1) atoms.
Nb3Cr8Al 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 Cr(1), three equivalent Cr(4), and six equivalent Cr(2) atoms. The Nb(1)-Nb(3) bond length is 3.01 Å. All Nb(1)-Nb(2) bond lengths are 3.00 Å. All Nb(1)-Cr(1) bond lengths are 2.87 Å. All Nb(1)-Cr(4) bond lengths are 2.86 Å. All Nb(1)-Cr(2) bond lengths are 2.87 Å. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to three equivalent Nb(1), three equivalent Cr(2), three equivalent Cr(4), six equivalent Cr(1), and one Al(1) atom. All Nb(2)-Cr(2) bond lengths are 2.91 Å. All Nb(2)-Cr(4) bond lengths are 2.87 Å. All Nb(2)-Cr(1) bond lengths are 2.85 Å. The Nb(2)-Al(1) bond length is 2.95 Å. In the third Nb site, Nb(3) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Cr(1), three equivalent Cr(3), six equivalent Cr(2), and three equivalent Al(1) atoms. All Nb(3)-Cr(1) bond lengths are 2.82 Å. All Nb(3)-Cr(3) bond lengths are 2.86 Å. All Nb(3)-Cr(2) bond lengths are 2.87 Å. All Nb(3)-Al(1) bond lengths are 2.98 Å. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Nb(1), one Nb(3), two equivalent Nb(2), one Cr(3), one Cr(4), four equivalent Cr(1), and two equivalent Al(1) atoms to form CrNb4Al2Cr6 cuboctahedra that share corners with two equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, corners with two equivalent Cr(4)Nb6Cr6 cuboctahedra, corners with four equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, corners with ten equivalent Cr(2)Nb5AlCr6 cuboctahedra, edges with two equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, edges with four equivalent Cr(2)Nb5AlCr6 cuboctahedra, faces with three equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, faces with three equivalent Cr(4)Nb6Cr6 cuboctahedra, faces with four equivalent Cr(2)Nb5AlCr6 cuboctahedra, and faces with eight equivalent Cr(1)Nb4Al2Cr6 cuboctahedra. The Cr(1)-Cr(3) bond length is 2.43 Å. The Cr(1)-Cr(4) bond length is 2.45 Å. All Cr(1)-Cr(1) bond lengths are 2.44 Å. Both Cr(1)-Al(1) bond lengths are 2.85 Å. In the second Cr site, Cr(2) is bonded to one Nb(2), two equivalent Nb(1), two equivalent Nb(3), one Cr(3), one Cr(4), four equivalent Cr(2), and one Al(1) atom to form CrNb5AlCr6 cuboctahedra that share corners with two equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, corners with two equivalent Cr(4)Nb6Cr6 cuboctahedra, corners with four equivalent Cr(2)Nb5AlCr6 cuboctahedra, corners with ten equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, edges with two equivalent Cr(2)Nb5AlCr6 cuboctahedra, edges with four equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, faces with three equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, faces with three equivalent Cr(4)Nb6Cr6 cuboctahedra, faces with four equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, and faces with eight equivalent Cr(2)Nb5AlCr6 cuboctahedra. The Cr(2)-Cr(3) bond length is 2.43 Å. The Cr(2)-Cr(4) bond length is 2.45 Å. There are two shorter (2.43 Å) and two longer (2.45 Å) Cr(2)-Cr(2) bond lengths. The Cr(2)-Al(1) bond length is 2.84 Å. In the third Cr site, Cr(3) is bonded to three equivalent Nb(3), three equivalent Cr(1), three equivalent Cr(2), and three equivalent Al(1) atoms to form CrNb3Al3Cr6 cuboctahedra that share corners with six equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, corners with six equivalent Cr(2)Nb5AlCr6 cuboctahedra, corners with six equivalent Cr(4)Nb6Cr6 cuboctahedra, edges with six equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, faces with nine equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, and faces with nine equivalent Cr(2)Nb5AlCr6 cuboctahedra. All Cr(3)-Al(1) bond lengths are 2.86 Å. In the fourth Cr site, Cr(4) is bonded to three equivalent Nb(1), three equivalent Nb(2), three equivalent Cr(1), and three equivalent Cr(2) atoms to form CrNb6Cr6 cuboctahedra that share corners with six equivalent Cr(3)Nb3Al3Cr6 cuboctahedra, corners with six equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, corners with six equivalent Cr(2)Nb5AlCr6 cuboctahedra, edges with six equivalent Cr(4)Nb6Cr6 cuboctahedra, faces with nine equivalent Cr(1)Nb4Al2Cr6 cuboctahedra, and faces with nine equivalent Cr(2)Nb5AlCr6 cuboctahedra. Al(1) is bonded in a 16-coordinate geometry to one Nb(2), three equivalent Nb(3), three equivalent Cr(2), three equivalent Cr(3), and six equivalent Cr(1) atoms.