Tl2HgSiSe4 crystallizes in the tetragonal I-42m space group. Hg(1) is bonded in a 4-coordinate geometry to four equivalent Se(1) atoms. Tl(1) is bonded in a 6-coordinate geometry to two equivalent Tl(1) and four equivalent Se(1) atoms. Si(1) is bonded in a tetrahedral geometry to four equivalent Se(1) atoms. Se(1) is bonded in a distorted L-shaped geometry to one Hg(1), two equivalent Tl(1), and one Si(1) atom.
Tl2HgSiSe4 crystallizes in the tetragonal I-42m space group. Hg(1) is bonded in a 4-coordinate geometry to four equivalent Se(1) atoms. All Hg(1)-Se(1) bond lengths are 2.75 Å. Tl(1) is bonded in a 6-coordinate geometry to two equivalent Tl(1) and four equivalent Se(1) atoms. Both Tl(1)-Tl(1) bond lengths are 3.43 Å. All Tl(1)-Se(1) bond lengths are 3.38 Å. Si(1) is bonded in a tetrahedral geometry to four equivalent Se(1) atoms. All Si(1)-Se(1) bond lengths are 2.32 Å. Se(1) is bonded in a distorted L-shaped geometry to one Hg(1), two equivalent Tl(1), and one Si(1) atom.