DOE OSTI2020
Fe3Ag(SnS4)2 is Spinel-derived structured and crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to four S2- atoms to form FeS4 tetrahedra that share corners with six equivalent FeS6 octahedra and corners with six equivalent SnS6 octahedra. The corner-sharing octahedra tilt angles range from 46–65°. There are two shorter (2.31 Å) and two longer (2.40 Å) Fe–S bond lengths. In the second Fe3+ site, Fe3+ is bonded to six S2- atoms to form FeS6 octahedra that share corners with three equivalent FeS4 tetrahedra, corners with three equivalent AgS4 tetrahedra, edges with two equivalent FeS6 octahedra, and edges with four equivalent SnS6 octahedra. There are a spread of Fe–S bond distances ranging from 2.25–2.42 Å. Ag1+ is bonded to four S2- atoms to form AgS4 tetrahedra that share corners with six equivalent FeS6 octahedra and corners with six equivalent SnS6 octahedra. The corner-sharing octahedra tilt angles range from 43–72°. There are two shorter (2.47 Å) and two longer (2.52 Å) Ag–S bond lengths. Sn3+ is bonded to six S2- atoms to form SnS6 octahedra that share corners with three equivalent FeS4 tetrahedra, corners with three equivalent AgS4 tetrahedra, edges with two equivalent SnS6 octahedra, and edges with four equivalent FeS6 octahedra. There are a spread of Sn–S bond distances ranging from 2.57–2.64 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two equivalent Sn3+ atoms. In the second S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Fe3+ and one Sn3+ atom. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Fe3+, one Ag1+, and two equivalent Sn3+ atoms. In the fourth S2- site, S2- is bonded to two equivalent Fe3+, one Ag1+, and one Sn3+ atom to form a mixture of distorted corner and edge-sharing SFe2AgSn trigonal pyramids.