Cs3HgCl5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to two equivalent Cl(1), two equivalent Cl(3), two equivalent Cl(4), and three equivalent Cl(2) atoms. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one Cl(3), one Cl(4), two equivalent Cl(1), and four equivalent Cl(2) atoms. Hg(1) is bonded in a tetrahedral geometry to one Cl(3), one Cl(4), and two equivalent Cl(2) atoms. There are four inequivalent Cl sites. In the first Cl site, Cl(4) is bonded to one Cs(2), four equivalent Cs(1), and one Hg(1) atom to form distorted ClCs5Hg octahedra that share corners with five equivalent Cl(1)Cs6 octahedra,  an edgeedge with one Cl(1)Cs6 octahedra, edges with two equivalent Cl(4)Cs5Hg octahedra, and  a faceface with one Cl(1)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 34-47°. In the second Cl site, Cl(1) is bonded to two equivalent Cs(2) and four equivalent Cs(1) atoms to form ClCs6 octahedra that share corners with five equivalent Cl(4)Cs5Hg octahedra,  an edgeedge with one Cl(4)Cs5Hg octahedra,  a faceface with one Cl(4)Cs5Hg octahedra, and faces with two equivalent Cl(1)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 34-47°. In the third Cl site, Cl(2) is bonded in a 6-coordinate geometry to two equivalent Cs(2), three equivalent Cs(1), and one Hg(1) atom. In the fourth Cl site, Cl(3) is bonded in a 6-coordinate geometry to one Cs(2), four equivalent Cs(1), and one Hg(1) atom.
Cs3HgCl5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to two equivalent Cl(1), two equivalent Cl(3), two equivalent Cl(4), and three equivalent Cl(2) atoms. There is one shorter (3.46 Å) and one longer (3.59 Å) Cs(1)-Cl(1) bond length. There is one shorter (3.90 Å) and one longer (3.98 Å) Cs(1)-Cl(3) bond length. There is one shorter (3.64 Å) and one longer (3.66 Å) Cs(1)-Cl(4) bond length. There are a spread of Cs(1)-Cl(2) bond distances ranging from 3.78-3.88 Å. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one Cl(3), one Cl(4), two equivalent Cl(1), and four equivalent Cl(2) atoms. The Cs(2)-Cl(3) bond length is 3.51 Å. The Cs(2)-Cl(4) bond length is 3.46 Å. There is one shorter (3.43 Å) and one longer (3.63 Å) Cs(2)-Cl(1) bond length. There are two shorter (3.37 Å) and two longer (3.67 Å) Cs(2)-Cl(2) bond lengths. Hg(1) is bonded in a tetrahedral geometry to one Cl(3), one Cl(4), and two equivalent Cl(2) atoms. The Hg(1)-Cl(3) bond length is 2.51 Å. The Hg(1)-Cl(4) bond length is 2.59 Å. Both Hg(1)-Cl(2) bond lengths are 2.48 Å. There are four inequivalent Cl sites. In the first Cl site, Cl(4) is bonded to one Cs(2), four equivalent Cs(1), and one Hg(1) atom to form distorted ClCs5Hg octahedra that share corners with five equivalent Cl(1)Cs6 octahedra,  an edgeedge with one Cl(1)Cs6 octahedra, edges with two equivalent Cl(4)Cs5Hg octahedra, and  a faceface with one Cl(1)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 34-47°. In the second Cl site, Cl(1) is bonded to two equivalent Cs(2) and four equivalent Cs(1) atoms to form ClCs6 octahedra that share corners with five equivalent Cl(4)Cs5Hg octahedra,  an edgeedge with one Cl(4)Cs5Hg octahedra,  a faceface with one Cl(4)Cs5Hg octahedra, and faces with two equivalent Cl(1)Cs6 octahedra. The corner-sharing octahedral tilt angles range from 34-47°. In the third Cl site, Cl(2) is bonded in a 6-coordinate geometry to two equivalent Cs(2), three equivalent Cs(1), and one Hg(1) atom. In the fourth Cl site, Cl(3) is bonded in a 6-coordinate geometry to one Cs(2), four equivalent Cs(1), and one Hg(1) atom.