Cs2HgBr4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Br(4), two equivalent Br(1), two equivalent Br(2), and three equivalent Br(3) atoms. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one Br(3), two equivalent Br(1), two equivalent Br(2), and three equivalent Br(4) atoms. Hg(1) is bonded in a tetrahedral geometry to one Br(1), one Br(2), one Br(3), and one Br(4) atom. There are four inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form a mixture of corner, face, and edge-sharing BrCs4Hg square pyramids. In the second Br site, Br(2) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form a mixture of corner, face, and edge-sharing BrCs4Hg square pyramids. In the third Br site, Br(3) is bonded in a 5-coordinate geometry to one Cs(2), three equivalent Cs(1), and one Hg(1) atom. In the fourth Br site, Br(4) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one Hg(1) atom.
Cs2HgBr4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Br(4), two equivalent Br(1), two equivalent Br(2), and three equivalent Br(3) atoms. The Cs(1)-Br(4) bond length is 3.91 Å. There is one shorter (3.77 Å) and one longer (3.80 Å) Cs(1)-Br(1) bond length. There is one shorter (3.76 Å) and one longer (3.84 Å) Cs(1)-Br(2) bond length. There are a spread of Cs(1)-Br(3) bond distances ranging from 3.92-4.15 Å. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one Br(3), two equivalent Br(1), two equivalent Br(2), and three equivalent Br(4) atoms. The Cs(2)-Br(3) bond length is 3.67 Å. There is one shorter (3.71 Å) and one longer (3.78 Å) Cs(2)-Br(1) bond length. There is one shorter (3.75 Å) and one longer (3.80 Å) Cs(2)-Br(2) bond length. There are a spread of Cs(2)-Br(4) bond distances ranging from 3.69-4.18 Å. Hg(1) is bonded in a tetrahedral geometry to one Br(1), one Br(2), one Br(3), and one Br(4) atom. The Hg(1)-Br(1) bond length is 2.68 Å. The Hg(1)-Br(2) bond length is 2.67 Å. The Hg(1)-Br(3) bond length is 2.68 Å. The Hg(1)-Br(4) bond length is 2.66 Å. There are four inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form a mixture of corner, face, and edge-sharing BrCs4Hg square pyramids. In the second Br site, Br(2) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Hg(1) atom to form a mixture of corner, face, and edge-sharing BrCs4Hg square pyramids. In the third Br site, Br(3) is bonded in a 5-coordinate geometry to one Cs(2), three equivalent Cs(1), and one Hg(1) atom. In the fourth Br site, Br(4) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one Hg(1) atom.