Al(CuSe2)3 crystallizes in the tetragonal I-42d space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, and corners with two equivalent Al(1)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to four equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra and corners with four equivalent Al(1)Se4 tetrahedra. Al(1) is bonded to four equivalent Se(2) atoms to form AlSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra and corners with four equivalent Cu(2)Se4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a water-like geometry to two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one Cu(1), one Cu(2), and one Al(1) atom.
Al(CuSe2)3 crystallizes in the tetragonal I-42d space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, and corners with two equivalent Al(1)Se4 tetrahedra. Both Cu(1)-Se(1) bond lengths are 2.32 Å. Both Cu(1)-Se(2) bond lengths are 2.39 Å. In the second Cu site, Cu(2) is bonded to four equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra and corners with four equivalent Al(1)Se4 tetrahedra. All Cu(2)-Se(2) bond lengths are 2.39 Å. Al(1) is bonded to four equivalent Se(2) atoms to form AlSe4 tetrahedra that share corners with four equivalent Cu(1)Se4 tetrahedra and corners with four equivalent Cu(2)Se4 tetrahedra. All Al(1)-Se(2) bond lengths are 2.41 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a water-like geometry to two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one Cu(1), one Cu(2), and one Al(1) atom.