DOE OSTI2020
Cr12Fe3S20 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are six inequivalent Cr+2.83+ sites. In the first Cr+2.83+ site, Cr+2.83+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with twelve CrS6 octahedra, edges with two FeS6 octahedra, and faces with two CrS6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Cr–S bond distances ranging from 2.36–2.40 Å. In the second Cr+2.83+ site, Cr+2.83+ is bonded to six S2- atoms to form CrS6 octahedra that share a cornercorner with one CrS6 octahedra, corners with five FeS6 octahedra, edges with six CrS6 octahedra, and a faceface with one CrS6 octahedra. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Cr–S bond distances ranging from 2.28–2.48 Å. In the third Cr+2.83+ site, Cr+2.83+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with three equivalent CrS6 octahedra, corners with three FeS6 octahedra, edges with six CrS6 octahedra, and a faceface with one FeS6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Cr–S bond distances ranging from 2.26–2.46 Å. In the fourth Cr+2.83+ site, Cr+2.83+ is bonded to six S2- atoms to form distorted CrS6 octahedra that share corners with two equivalent FeS6 octahedra, corners with four equivalent CrS6 octahedra, edges with six CrS6 octahedra, and a faceface with one FeS6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Cr–S bond distances ranging from 2.25–2.46 Å. In the fifth Cr+2.83+ site, Cr+2.83+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with three equivalent CrS6 octahedra, corners with three FeS6 octahedra, edges with six CrS6 octahedra, and a faceface with one FeS6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are a spread of Cr–S bond distances ranging from 2.27–2.47 Å. In the sixth Cr+2.83+ site, Cr+2.83+ is bonded to six S2- atoms to form distorted CrS6 octahedra that share a cornercorner with one CrS6 octahedra, corners with five FeS6 octahedra, edges with six CrS6 octahedra, and a faceface with one CrS6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Cr–S bond distances ranging from 2.25–2.49 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six S2- atoms to form FeS6 octahedra that share corners with twelve CrS6 octahedra, an edgeedge with one CrS6 octahedra, an edgeedge with one FeS6 octahedra, and faces with two CrS6 octahedra. The corner-sharing octahedra tilt angles range from 48–55°. There are a spread of Fe–S bond distances ranging from 2.27–2.49 Å. In the second Fe2+ site, Fe2+ is bonded to six S2- atoms to form FeS6 octahedra that share corners with twelve CrS6 octahedra, edges with two equivalent CrS6 octahedra, and faces with two equivalent CrS6 octahedra. The corner-sharing octahedra tilt angles range from 52–54°. There are two shorter (2.29 Å) and four longer (2.36 Å) Fe–S bond lengths. There are ten inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to four Cr+2.83+ and one Fe2+ atom. In the second S2- site, S2- is bonded in a 5-coordinate geometry to three Cr+2.83+ and two equivalent Fe2+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to four Cr+2.83+ and one Fe2+ atom. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to four Cr+2.83+ and one Fe2+ atom. In the fifth S2- site, S2- is bonded in a 5-coordinate geometry to four Cr+2.83+ and one Fe2+ atom. In the sixth S2- site, S2- is bonded in a 4-coordinate geometry to three Cr+2.83+ and one Fe2+ atom. In the seventh S2- site, S2- is bonded in a 4-coordinate geometry to four Cr+2.83+ atoms. In the eighth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Cr+2.83+ and one Fe2+ atom. In the ninth S2- site, S2- is bonded in a 4-coordinate geometry to three Cr+2.83+ and one Fe2+ atom. In the tenth S2- site, S2- is bonded in a 4-coordinate geometry to four Cr+2.83+ atoms.