DOE OSTI2020
HgBi2S4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded to six S2- atoms to form distorted HgS6 octahedra that share corners with two equivalent BiS6 octahedra, corners with four equivalent BiS7 square pyramids, edges with two equivalent HgS6 octahedra, and edges with six equivalent BiS7 square pyramids. The corner-sharing octahedral tilt angles are 66°. There are two shorter (2.40 Å) and four longer (3.24 Å) Hg–S bond lengths. In the second Hg2+ site, Hg2+ is bonded to six S2- atoms to form distorted HgS6 octahedra that share corners with four equivalent BiS6 octahedra, corners with four equivalent BiS7 square pyramids, edges with two equivalent HgS6 octahedra, and edges with six equivalent BiS6 octahedra. The corner-sharing octahedral tilt angles are 8°. There are two shorter (2.39 Å) and four longer (3.27 Å) Hg–S bond lengths. There are two inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six S2- atoms to form BiS6 octahedra that share corners with three HgS6 octahedra, corners with four equivalent BiS7 square pyramids, edges with three equivalent HgS6 octahedra, edges with four equivalent BiS6 octahedra, and an edgeedge with one BiS7 square pyramid. The corner-sharing octahedra tilt angles range from 8–66°. There are a spread of Bi–S bond distances ranging from 2.65–3.17 Å. In the second Bi3+ site, Bi3+ is bonded to seven S2- atoms to form distorted BiS7 square pyramids that share corners with four HgS6 octahedra, corners with four equivalent BiS6 octahedra, an edgeedge with one BiS6 octahedra, edges with three equivalent HgS6 octahedra, edges with two equivalent BiS7 square pyramids, and faces with two equivalent BiS7 square pyramids. The corner-sharing octahedra tilt angles range from 9–64°. There are a spread of Bi–S bond distances ranging from 2.62–3.48 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to one Hg2+ and four Bi3+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Hg2+ and three equivalent Bi3+ atoms. In the third S2- site, S2- is bonded to one Hg2+ and three Bi3+ atoms to form distorted SHgBi3 tetrahedra that share corners with three equivalent SHg2Bi3 square pyramids and corners with three equivalent SHgBi3 tetrahedra. In the fourth S2- site, S2- is bonded to two equivalent Hg2+ and three equivalent Bi3+ atoms to form distorted SHg2Bi3 square pyramids that share corners with two equivalent SHg2Bi3 square pyramids, corners with three equivalent SHgBi3 tetrahedra, and edges with five equivalent SHg2Bi3 square pyramids.