Al4Cu9 is gamma-brass-like structured and crystallizes in the cubic P-43m space group. There are six inequivalent Cu sites. In the first Cu site, Cu(5) is bonded in a 12-coordinate geometry to three equivalent Cu(2), three equivalent Cu(4), three equivalent Al(1), and three equivalent Al(2) atoms. In the second Cu site, Cu(6) is bonded in a 12-coordinate geometry to three equivalent Cu(1), three equivalent Cu(3), three equivalent Cu(6), and three equivalent Al(2) atoms. In the third Cu site, Cu(1) is bonded in a 3-coordinate geometry to three equivalent Cu(3), three equivalent Cu(4), three equivalent Cu(6), and three equivalent Al(2) atoms. In the fourth Cu site, Cu(2) is bonded in a 13-coordinate geometry to one Cu(2), two equivalent Cu(5), four equivalent Cu(4), two equivalent Al(1), and four equivalent Al(2) atoms. In the fifth Cu site, Cu(3) is bonded in a 13-coordinate geometry to one Cu(3), two equivalent Cu(1), two equivalent Cu(6), four equivalent Cu(4), and four equivalent Al(2) atoms. In the sixth Cu site, Cu(4) is bonded in a 11-coordinate geometry to one Cu(1), one Cu(5), two equivalent Cu(2), two equivalent Cu(3), one Al(1), and four equivalent Al(2) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 9-coordinate geometry to three equivalent Cu(2), three equivalent Cu(4), and three equivalent Cu(5) atoms. In the second Al site, Al(2) is bonded in a 11-coordinate geometry to one Cu(1), one Cu(5), one Cu(6), two equivalent Cu(2), two equivalent Cu(3), and four equivalent Cu(4) atoms.
Al4Cu9 is gamma-brass-like structured and crystallizes in the cubic P-43m space group. There are six inequivalent Cu sites. In the first Cu site, Cu(5) is bonded in a 12-coordinate geometry to three equivalent Cu(2), three equivalent Cu(4), three equivalent Al(1), and three equivalent Al(2) atoms. All Cu(5)-Cu(2) bond lengths are 2.62 Å. All Cu(5)-Cu(4) bond lengths are 2.49 Å. All Cu(5)-Al(1) bond lengths are 2.58 Å. All Cu(5)-Al(2) bond lengths are 2.55 Å. In the second Cu site, Cu(6) is bonded in a 12-coordinate geometry to three equivalent Cu(1), three equivalent Cu(3), three equivalent Cu(6), and three equivalent Al(2) atoms. All Cu(6)-Cu(1) bond lengths are 2.54 Å. All Cu(6)-Cu(3) bond lengths are 2.50 Å. All Cu(6)-Cu(6) bond lengths are 2.56 Å. All Cu(6)-Al(2) bond lengths are 2.56 Å. In the third Cu site, Cu(1) is bonded in a 3-coordinate geometry to three equivalent Cu(3), three equivalent Cu(4), three equivalent Cu(6), and three equivalent Al(2) atoms. All Cu(1)-Cu(3) bond lengths are 2.63 Å. All Cu(1)-Cu(4) bond lengths are 2.54 Å. All Cu(1)-Al(2) bond lengths are 2.44 Å. In the fourth Cu site, Cu(2) is bonded in a 13-coordinate geometry to one Cu(2), two equivalent Cu(5), four equivalent Cu(4), two equivalent Al(1), and four equivalent Al(2) atoms. The Cu(2)-Cu(2) bond length is 2.49 Å. All Cu(2)-Cu(4) bond lengths are 2.76 Å. Both Cu(2)-Al(1) bond lengths are 2.50 Å. There are two shorter (2.51 Å) and two longer (2.79 Å) Cu(2)-Al(2) bond lengths. In the fifth Cu site, Cu(3) is bonded in a 13-coordinate geometry to one Cu(3), two equivalent Cu(1), two equivalent Cu(6), four equivalent Cu(4), and four equivalent Al(2) atoms. The Cu(3)-Cu(3) bond length is 2.51 Å. There are two shorter (2.45 Å) and two longer (2.72 Å) Cu(3)-Cu(4) bond lengths. All Cu(3)-Al(2) bond lengths are 2.71 Å. In the sixth Cu site, Cu(4) is bonded in a 11-coordinate geometry to one Cu(1), one Cu(5), two equivalent Cu(2), two equivalent Cu(3), one Al(1), and four equivalent Al(2) atoms. The Cu(4)-Al(1) bond length is 2.50 Å. There are two shorter (2.55 Å) and two longer (2.57 Å) Cu(4)-Al(2) bond lengths. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 9-coordinate geometry to three equivalent Cu(2), three equivalent Cu(4), and three equivalent Cu(5) atoms. In the second Al site, Al(2) is bonded in a 11-coordinate geometry to one Cu(1), one Cu(5), one Cu(6), two equivalent Cu(2), two equivalent Cu(3), and four equivalent Cu(4) atoms.