DOE OSTI2020
U8FeS17 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent U+3.88+ sites. In the first U+3.88+ site, U+3.88+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of U–S bond distances ranging from 2.71–2.78 Å. In the second U+3.88+ site, U+3.88+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of U–S bond distances ranging from 2.70–2.88 Å. In the third U+3.88+ site, U+3.88+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of U–S bond distances ranging from 2.70–2.98 Å. Fe3+ is bonded in an octahedral geometry to six S2- atoms. There are two shorter (2.25 Å) and four longer (2.35 Å) Fe–S bond lengths. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to six U+3.88+ atoms to form corner-sharing SU6 octahedra. In the second S2- site, S2- is bonded to four U+3.88+ atoms to form distorted SU4 trigonal pyramids that share corners with two equivalent SU6 octahedra, corners with six equivalent SU3Fe trigonal pyramids, and edges with three SU4 trigonal pyramids. The corner-sharing octahedral tilt angles are 38°. In the third S2- site, S2- is bonded to three U+3.88+ and one Fe3+ atom to form distorted SU3Fe trigonal pyramids that share a cornercorner with one SU6 octahedra, corners with eight SU4 trigonal pyramids, and edges with three SU4 trigonal pyramids. The corner-sharing octahedral tilt angles are 53°. In the fourth S2- site, S2- is bonded in a rectangular see-saw-like geometry to four U+3.88+ atoms. In the fifth S2- site, S2- is bonded in a rectangular see-saw-like geometry to four U+3.88+ atoms. In the sixth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four U+3.88+ atoms. In the seventh S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three U+3.88+ and one Fe3+ atom.