Cs2HgF4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. Cs(1) is bonded in a 9-coordinate geometry to four equivalent F(2) and five equivalent F(1) atoms. Hg(1) is bonded to two equivalent F(1) and four equivalent F(2) atoms to form corner-sharing HgF6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent F sites. In the first F site, F(2) is bonded to four equivalent Cs(1) and two equivalent Hg(1) atoms to form FCs4Hg2 octahedra that share corners with two equivalent F(2)Cs4Hg2 octahedra, corners with twelve equivalent F(1)Cs5Hg octahedra, edges with two equivalent F(2)Cs4Hg2 octahedra, faces with four equivalent F(2)Cs4Hg2 octahedra, and faces with four equivalent F(1)Cs5Hg octahedra. The corner-sharing octahedral tilt angles range from 0-56°. In the second F site, F(1) is bonded to five equivalent Cs(1) and one Hg(1) atom to form distorted FCs5Hg octahedra that share corners with five equivalent F(1)Cs5Hg octahedra, corners with twelve equivalent F(2)Cs4Hg2 octahedra, edges with eight equivalent F(1)Cs5Hg octahedra, and faces with four equivalent F(2)Cs4Hg2 octahedra. The corner-sharing octahedral tilt angles range from 0-56°.
Cs2HgF4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. Cs(1) is bonded in a 9-coordinate geometry to four equivalent F(2) and five equivalent F(1) atoms. All Cs(1)-F(2) bond lengths are 3.12 Å. There is one shorter (2.92 Å) and four longer (3.29 Å) Cs(1)-F(1) bond lengths. Hg(1) is bonded to two equivalent F(1) and four equivalent F(2) atoms to form corner-sharing HgF6 octahedra. The corner-sharing octahedra are not tilted. Both Hg(1)-F(1) bond lengths are 2.25 Å. All Hg(1)-F(2) bond lengths are 2.33 Å. There are two inequivalent F sites. In the first F site, F(2) is bonded to four equivalent Cs(1) and two equivalent Hg(1) atoms to form FCs4Hg2 octahedra that share corners with two equivalent F(2)Cs4Hg2 octahedra, corners with twelve equivalent F(1)Cs5Hg octahedra, edges with two equivalent F(2)Cs4Hg2 octahedra, faces with four equivalent F(2)Cs4Hg2 octahedra, and faces with four equivalent F(1)Cs5Hg octahedra. The corner-sharing octahedral tilt angles range from 0-56°. In the second F site, F(1) is bonded to five equivalent Cs(1) and one Hg(1) atom to form distorted FCs5Hg octahedra that share corners with five equivalent F(1)Cs5Hg octahedra, corners with twelve equivalent F(2)Cs4Hg2 octahedra, edges with eight equivalent F(1)Cs5Hg octahedra, and faces with four equivalent F(2)Cs4Hg2 octahedra. The corner-sharing octahedral tilt angles range from 0-56°.