Cs2HgI4 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one I(3), two equivalent I(1), two equivalent I(4), and three equivalent I(2) atoms. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one I(2), two equivalent I(1), two equivalent I(4), and three equivalent I(3) atoms. Hg(1) is bonded in a tetrahedral geometry to one I(1), one I(2), one I(3), and one I(4) atom. There are four inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Cs(2), three equivalent Cs(1), and one Hg(1) atom. In the third I site, I(3) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one Hg(1) atom. In the fourth I site, I(4) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form distorted corner-sharing ICs4Hg square pyramids.
Cs2HgI4 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one I(3), two equivalent I(1), two equivalent I(4), and three equivalent I(2) atoms. The Cs(1)-I(3) bond length is 4.06 Å. There is one shorter (4.05 Å) and one longer (4.07 Å) Cs(1)-I(1) bond length. There is one shorter (4.10 Å) and one longer (4.12 Å) Cs(1)-I(4) bond length. There are a spread of Cs(1)-I(2) bond distances ranging from 4.01-4.44 Å. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one I(2), two equivalent I(1), two equivalent I(4), and three equivalent I(3) atoms. The Cs(2)-I(2) bond length is 3.86 Å. There is one shorter (4.03 Å) and one longer (4.23 Å) Cs(2)-I(1) bond length. There is one shorter (4.00 Å) and one longer (4.13 Å) Cs(2)-I(4) bond length. There are a spread of Cs(2)-I(3) bond distances ranging from 4.04-4.43 Å. Hg(1) is bonded in a tetrahedral geometry to one I(1), one I(2), one I(3), and one I(4) atom. The Hg(1)-I(1) bond length is 2.85 Å. The Hg(1)-I(2) bond length is 2.83 Å. The Hg(1)-I(3) bond length is 2.90 Å. The Hg(1)-I(4) bond length is 2.84 Å. There are four inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Cs(2), three equivalent Cs(1), and one Hg(1) atom. In the third I site, I(3) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one Hg(1) atom. In the fourth I site, I(4) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form distorted corner-sharing ICs4Hg square pyramids.