Cu15Al4 crystallizes in the tetragonal P4/mmm space group. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a body-centered cubic geometry to eight equivalent Cu(4) atoms. In the second Cu site, Cu(2) is bonded to four equivalent Cu(4), four equivalent Cu(5), and four equivalent Al(1) atoms to form distorted CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(2)Al4Cu8 cuboctahedra, corners with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with four equivalent Al(2)Cu12 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra,  a faceface with one Cu(3)Al4Cu8 cuboctahedra, faces with four equivalent Cu(2)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, and faces with four equivalent Al(1)Cu12 cuboctahedra. In the third Cu site, Cu(3) is bonded to four equivalent Cu(5), four equivalent Cu(6), and four equivalent Al(2) atoms to form distorted CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(2)Al4Cu8 cuboctahedra, corners with eight equivalent Cu(3)Al4Cu8 cuboctahedra, edges with four equivalent Al(1)Cu12 cuboctahedra, edges with four equivalent Al(2)Cu12 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(6)Al4Cu8 cuboctahedra,  a faceface with one Cu(2)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, faces with four equivalent Cu(6)Al4Cu8 cuboctahedra, faces with four equivalent Al(2)Cu12 cuboctahedra, and faces with five equivalent Cu(3)Al4Cu8 cuboctahedra. In the fourth Cu site, Cu(4) is bonded in a 10-coordinate geometry to two equivalent Cu(1), two equivalent Cu(2), four equivalent Cu(4), and two equivalent Al(1) atoms. In the fifth Cu site, Cu(5) is bonded to two equivalent Cu(2), two equivalent Cu(3), four equivalent Cu(5), two equivalent Al(1), and two equivalent Al(2) atoms to form CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(5)Al4Cu8 cuboctahedra, corners with four equivalent Cu(6)Al4Cu8 cuboctahedra, edges with four equivalent Cu(2)Al4Cu8 cuboctahedra, edges with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with four equivalent Cu(6)Al4Cu8 cuboctahedra, edges with four equivalent Al(1)Cu12 cuboctahedra, edges with four equivalent Al(2)Cu12 cuboctahedra,  a faceface with one Cu(6)Al4Cu8 cuboctahedra, faces with two equivalent Cu(2)Al4Cu8 cuboctahedra, faces with two equivalent Cu(3)Al4Cu8 cuboctahedra, faces with two equivalent Al(1)Cu12 cuboctahedra, faces with two equivalent Al(2)Cu12 cuboctahedra, and faces with eight equivalent Cu(5)Al4Cu8 cuboctahedra. In the sixth Cu site, Cu(6) is bonded to four equivalent Cu(3), four equivalent Cu(6), and four equivalent Al(2) atoms to form CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(6)Al4Cu8 cuboctahedra, corners with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(3)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Al(2)Cu12 cuboctahedra, faces with two equivalent Cu(5)Al4Cu8 cuboctahedra, faces with four equivalent Cu(3)Al4Cu8 cuboctahedra, faces with four equivalent Al(2)Cu12 cuboctahedra, and faces with eight equivalent Cu(6)Al4Cu8 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Cu(2), four equivalent Cu(4), and four equivalent Cu(5) atoms to form AlCu12 cuboctahedra that share corners with four equivalent Al(1)Cu12 cuboctahedra, corners with four equivalent Al(2)Cu12 cuboctahedra, edges with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra,  a faceface with one Al(2)Cu12 cuboctahedra, faces with four equivalent Cu(2)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, and faces with four equivalent Al(1)Cu12 cuboctahedra. In the second Al site, Al(2) is bonded to four equivalent Cu(3), four equivalent Cu(5), and four equivalent Cu(6) atoms to form AlCu12 cuboctahedra that share corners with four equivalent Al(1)Cu12 cuboctahedra, corners with eight equivalent Al(2)Cu12 cuboctahedra, edges with four equivalent Cu(2)Al4Cu8 cuboctahedra, edges with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(6)Al4Cu8 cuboctahedra,  a faceface with one Al(1)Cu12 cuboctahedra, faces with four equivalent Cu(3)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, faces with four equivalent Cu(6)Al4Cu8 cuboctahedra, and faces with five equivalent Al(2)Cu12 cuboctahedra.
Cu15Al4 crystallizes in the tetragonal P4/mmm space group. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a body-centered cubic geometry to eight equivalent Cu(4) atoms. All Cu(1)-Cu(4) bond lengths are 2.45 Å. In the second Cu site, Cu(2) is bonded to four equivalent Cu(4), four equivalent Cu(5), and four equivalent Al(1) atoms to form distorted CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(2)Al4Cu8 cuboctahedra, corners with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with four equivalent Al(2)Cu12 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra,  a faceface with one Cu(3)Al4Cu8 cuboctahedra, faces with four equivalent Cu(2)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, and faces with four equivalent Al(1)Cu12 cuboctahedra. All Cu(2)-Cu(4) bond lengths are 2.58 Å. All Cu(2)-Cu(5) bond lengths are 2.62 Å. All Cu(2)-Al(1) bond lengths are 2.55 Å. In the third Cu site, Cu(3) is bonded to four equivalent Cu(5), four equivalent Cu(6), and four equivalent Al(2) atoms to form distorted CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(2)Al4Cu8 cuboctahedra, corners with eight equivalent Cu(3)Al4Cu8 cuboctahedra, edges with four equivalent Al(1)Cu12 cuboctahedra, edges with four equivalent Al(2)Cu12 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(6)Al4Cu8 cuboctahedra,  a faceface with one Cu(2)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, faces with four equivalent Cu(6)Al4Cu8 cuboctahedra, faces with four equivalent Al(2)Cu12 cuboctahedra, and faces with five equivalent Cu(3)Al4Cu8 cuboctahedra. All Cu(3)-Cu(5) bond lengths are 2.63 Å. All Cu(3)-Cu(6) bond lengths are 2.63 Å. All Cu(3)-Al(2) bond lengths are 2.55 Å. In the fourth Cu site, Cu(4) is bonded in a 10-coordinate geometry to two equivalent Cu(1), two equivalent Cu(2), four equivalent Cu(4), and two equivalent Al(1) atoms. All Cu(4)-Cu(4) bond lengths are 2.55 Å. Both Cu(4)-Al(1) bond lengths are 2.59 Å. In the fifth Cu site, Cu(5) is bonded to two equivalent Cu(2), two equivalent Cu(3), four equivalent Cu(5), two equivalent Al(1), and two equivalent Al(2) atoms to form CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(5)Al4Cu8 cuboctahedra, corners with four equivalent Cu(6)Al4Cu8 cuboctahedra, edges with four equivalent Cu(2)Al4Cu8 cuboctahedra, edges with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with four equivalent Cu(6)Al4Cu8 cuboctahedra, edges with four equivalent Al(1)Cu12 cuboctahedra, edges with four equivalent Al(2)Cu12 cuboctahedra,  a faceface with one Cu(6)Al4Cu8 cuboctahedra, faces with two equivalent Cu(2)Al4Cu8 cuboctahedra, faces with two equivalent Cu(3)Al4Cu8 cuboctahedra, faces with two equivalent Al(1)Cu12 cuboctahedra, faces with two equivalent Al(2)Cu12 cuboctahedra, and faces with eight equivalent Cu(5)Al4Cu8 cuboctahedra. All Cu(5)-Cu(5) bond lengths are 2.55 Å. Both Cu(5)-Al(1) bond lengths are 2.60 Å. Both Cu(5)-Al(2) bond lengths are 2.63 Å. In the sixth Cu site, Cu(6) is bonded to four equivalent Cu(3), four equivalent Cu(6), and four equivalent Al(2) atoms to form CuAl4Cu8 cuboctahedra that share corners with four equivalent Cu(6)Al4Cu8 cuboctahedra, corners with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(3)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Al(2)Cu12 cuboctahedra, faces with two equivalent Cu(5)Al4Cu8 cuboctahedra, faces with four equivalent Cu(3)Al4Cu8 cuboctahedra, faces with four equivalent Al(2)Cu12 cuboctahedra, and faces with eight equivalent Cu(6)Al4Cu8 cuboctahedra. All Cu(6)-Cu(6) bond lengths are 2.55 Å. All Cu(6)-Al(2) bond lengths are 2.63 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Cu(2), four equivalent Cu(4), and four equivalent Cu(5) atoms to form AlCu12 cuboctahedra that share corners with four equivalent Al(1)Cu12 cuboctahedra, corners with four equivalent Al(2)Cu12 cuboctahedra, edges with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra,  a faceface with one Al(2)Cu12 cuboctahedra, faces with four equivalent Cu(2)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, and faces with four equivalent Al(1)Cu12 cuboctahedra. In the second Al site, Al(2) is bonded to four equivalent Cu(3), four equivalent Cu(5), and four equivalent Cu(6) atoms to form AlCu12 cuboctahedra that share corners with four equivalent Al(1)Cu12 cuboctahedra, corners with eight equivalent Al(2)Cu12 cuboctahedra, edges with four equivalent Cu(2)Al4Cu8 cuboctahedra, edges with four equivalent Cu(3)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(5)Al4Cu8 cuboctahedra, edges with eight equivalent Cu(6)Al4Cu8 cuboctahedra,  a faceface with one Al(1)Cu12 cuboctahedra, faces with four equivalent Cu(3)Al4Cu8 cuboctahedra, faces with four equivalent Cu(5)Al4Cu8 cuboctahedra, faces with four equivalent Cu(6)Al4Cu8 cuboctahedra, and faces with five equivalent Al(2)Cu12 cuboctahedra.