HgAl2Se4 crystallizes in the tetragonal I-4 space group. Hg(1) is bonded to four equivalent Se(1) atoms to form HgSe4 tetrahedra that share 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 four equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with four equivalent Hg(1)Se4 tetrahedra and corners with four equivalent Al(2)Se4 tetrahedra. In the second Al site, Al(2) is bonded to four equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with four equivalent Hg(1)Se4 tetrahedra and corners with four equivalent Al(1)Se4 tetrahedra. Se(1) is bonded in a trigonal non-coplanar geometry to one Hg(1), one Al(1), and one Al(2) atom.
HgAl2Se4 crystallizes in the tetragonal I-4 space group. Hg(1) is bonded to four equivalent Se(1) atoms to form HgSe4 tetrahedra that share corners with four equivalent Al(1)Se4 tetrahedra and corners with four equivalent Al(2)Se4 tetrahedra. All Hg(1)-Se(1) bond lengths are 2.68 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with four equivalent Hg(1)Se4 tetrahedra and corners with four equivalent Al(2)Se4 tetrahedra. All Al(1)-Se(1) bond lengths are 2.40 Å. In the second Al site, Al(2) is bonded to four equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with four equivalent Hg(1)Se4 tetrahedra and corners with four equivalent Al(1)Se4 tetrahedra. All Al(2)-Se(1) bond lengths are 2.40 Å. Se(1) is bonded in a trigonal non-coplanar geometry to one Hg(1), one Al(1), and one Al(2) atom.