ZnAl2Se4 crystallizes in the monoclinic Pm space group. Zn(1) is bonded to one Se(1), one Se(4), and two equivalent Se(3) atoms to form ZnSe4 tetrahedra that share corners with two equivalent Zn(1)Se4 tetrahedra, corners with four equivalent Al(1)Se4 tetrahedra, and corners with four equivalent Al(2)Se4 tetrahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one Se(2), one Se(3), and two equivalent Se(4) atoms to form AlSe4 tetrahedra that share corners with two equivalent Al(1)Se4 tetrahedra, corners with two equivalent Al(2)Se4 tetrahedra, and corners with four equivalent Zn(1)Se4 tetrahedra. In the second Al site, Al(2) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with two equivalent Al(1)Se4 tetrahedra, corners with two equivalent Al(2)Se4 tetrahedra, and corners with four equivalent Zn(1)Se4 tetrahedra. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one Zn(1) and two equivalent Al(2) atoms. In the second Se site, Se(2) is bonded in a water-like geometry to one Al(1) and one Al(2) atom. In the third Se site, Se(3) is bonded to two equivalent Zn(1), one Al(1), and one Al(2) atom to form corner-sharing SeAl2Zn2 tetrahedra. In the fourth Se site, Se(4) is bonded in a trigonal non-coplanar geometry to one Zn(1) and two equivalent Al(1) atoms.
ZnAl2Se4 crystallizes in the monoclinic Pm space group. Zn(1) is bonded to one Se(1), one Se(4), and two equivalent Se(3) atoms to form ZnSe4 tetrahedra that share corners with two equivalent Zn(1)Se4 tetrahedra, corners with four equivalent Al(1)Se4 tetrahedra, and corners with four equivalent Al(2)Se4 tetrahedra. The Zn(1)-Se(1) bond length is 2.47 Å. The Zn(1)-Se(4) bond length is 2.48 Å. Both Zn(1)-Se(3) bond lengths are 2.53 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one Se(2), one Se(3), and two equivalent Se(4) atoms to form AlSe4 tetrahedra that share corners with two equivalent Al(1)Se4 tetrahedra, corners with two equivalent Al(2)Se4 tetrahedra, and corners with four equivalent Zn(1)Se4 tetrahedra. The Al(1)-Se(2) bond length is 2.34 Å. The Al(1)-Se(3) bond length is 2.51 Å. Both Al(1)-Se(4) bond lengths are 2.45 Å. In the second Al site, Al(2) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with two equivalent Al(1)Se4 tetrahedra, corners with two equivalent Al(2)Se4 tetrahedra, and corners with four equivalent Zn(1)Se4 tetrahedra. The Al(2)-Se(2) bond length is 2.32 Å. The Al(2)-Se(3) bond length is 2.55 Å. Both Al(2)-Se(1) bond lengths are 2.44 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one Zn(1) and two equivalent Al(2) atoms. In the second Se site, Se(2) is bonded in a water-like geometry to one Al(1) and one Al(2) atom. In the third Se site, Se(3) is bonded to two equivalent Zn(1), one Al(1), and one Al(2) atom to form corner-sharing SeAl2Zn2 tetrahedra. In the fourth Se site, Se(4) is bonded in a trigonal non-coplanar geometry to one Zn(1) and two equivalent Al(1) atoms.