DOE OSTI2020
U8CrS17 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 2.73–2.89 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 2.72–2.82 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 2.69–2.97 Å. Cr3+ is bonded in an octahedral geometry to six S2- atoms. There are two shorter (2.32 Å) and four longer (2.42 Å) Cr–S bond lengths. There are seven inequivalent S2- sites. In the first 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 SU3Cr tetrahedra, edges with two equivalent SU3Cr tetrahedra, and an edgeedge with one SU4 trigonal pyramid. The corner-sharing octahedral tilt angles are 38°. In the second S2- site, S2- is bonded to six U+3.88+ atoms to form SU6 octahedra that share corners with four equivalent SU3Cr tetrahedra and corners with four equivalent SU4 trigonal pyramids. In the third S2- site, S2- is bonded in a rectangular see-saw-like geometry to four U+3.88+ atoms. In the fourth S2- site, S2- is bonded to three U+3.88+ and one Cr3+ atom to form distorted SU3Cr tetrahedra that share a cornercorner with one SU6 octahedra, corners with five equivalent SU3Cr tetrahedra, corners with three equivalent SU4 trigonal pyramids, edges with two equivalent SU3Cr tetrahedra, and an edgeedge with one SU4 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. 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 three U+3.88+ and one Cr3+ atom. In the seventh S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four U+3.88+ atoms.