Cs2HgCl4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Cl(1), three equivalent Cl(2), and four equivalent Cl(3) atoms. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to two equivalent Cl(2), three equivalent Cl(1), and four equivalent Cl(3) atoms. Hg(1) is bonded in a tetrahedral geometry to one Cl(1), one Cl(2), and two equivalent Cl(3) atoms. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one Hg(1) atom. In the second Cl site, Cl(2) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Hg(1) atom to form distorted ClCs5Hg octahedra that share corners with four equivalent Cl(2)Cs5Hg octahedra, corners with six equivalent Cl(3)Cs4Hg square pyramids, edges with two equivalent Cl(2)Cs5Hg octahedra, edges with two equivalent Cl(3)Cs4Hg square pyramids, and faces with four equivalent Cl(3)Cs4Hg square pyramids. The corner-sharing octahedral tilt angles range from 20-44°. In the third Cl site, Cl(3) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form distorted ClCs4Hg square pyramids that share corners with three equivalent Cl(2)Cs5Hg octahedra, corners with six equivalent Cl(3)Cs4Hg square pyramids,  an edgeedge with one Cl(2)Cs5Hg octahedra, edges with two equivalent Cl(3)Cs4Hg square pyramids, faces with two equivalent Cl(2)Cs5Hg octahedra, and  a faceface with one Cl(3)Cs4Hg square pyramid. The corner-sharing octahedral tilt angles range from 39-59°.
Cs2HgCl4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Cl(1), three equivalent Cl(2), and four equivalent Cl(3) atoms. The Cs(1)-Cl(1) bond length is 3.48 Å. There is one shorter (3.72 Å) and two longer (3.85 Å) Cs(1)-Cl(2) bond lengths. There are two shorter (3.63 Å) and two longer (3.67 Å) Cs(1)-Cl(3) bond lengths. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to two equivalent Cl(2), three equivalent Cl(1), and four equivalent Cl(3) atoms. There is one shorter (3.53 Å) and one longer (3.54 Å) Cs(2)-Cl(2) bond length. There is one shorter (3.60 Å) and two longer (4.02 Å) Cs(2)-Cl(1) bond lengths. There are two shorter (3.50 Å) and two longer (3.57 Å) Cs(2)-Cl(3) bond lengths. Hg(1) is bonded in a tetrahedral geometry to one Cl(1), one Cl(2), and two equivalent Cl(3) atoms. The Hg(1)-Cl(1) bond length is 2.46 Å. The Hg(1)-Cl(2) bond length is 2.55 Å. Both Hg(1)-Cl(3) bond lengths are 2.52 Å. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one Hg(1) atom. In the second Cl site, Cl(2) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Hg(1) atom to form distorted ClCs5Hg octahedra that share corners with four equivalent Cl(2)Cs5Hg octahedra, corners with six equivalent Cl(3)Cs4Hg square pyramids, edges with two equivalent Cl(2)Cs5Hg octahedra, edges with two equivalent Cl(3)Cs4Hg square pyramids, and faces with four equivalent Cl(3)Cs4Hg square pyramids. The corner-sharing octahedral tilt angles range from 20-44°. In the third Cl site, Cl(3) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form distorted ClCs4Hg square pyramids that share corners with three equivalent Cl(2)Cs5Hg octahedra, corners with six equivalent Cl(3)Cs4Hg square pyramids,  an edgeedge with one Cl(2)Cs5Hg octahedra, edges with two equivalent Cl(3)Cs4Hg square pyramids, faces with two equivalent Cl(2)Cs5Hg octahedra, and  a faceface with one Cl(3)Cs4Hg square pyramid. The corner-sharing octahedral tilt angles range from 39-59°.