DOE OSTI2020
U8MnSe17 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent U4+ sites. In the first U4+ site, U4+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of U–Se bond distances ranging from 2.89–3.04 Å. In the second U4+ site, U4+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of U–Se bond distances ranging from 2.86–2.93 Å. In the third U4+ site, U4+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of U–Se bond distances ranging from 2.80–3.08 Å. Mn2+ is bonded in an octahedral geometry to six Se2- atoms. There are two shorter (2.45 Å) and four longer (2.58 Å) Mn–Se bond lengths. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four U4+ atoms to form distorted SeU4 trigonal pyramids that share corners with two equivalent SeU6 octahedra, corners with six equivalent SeU3Mn tetrahedra, edges with two equivalent SeU3Mn tetrahedra, and an edgeedge with one SeU4 trigonal pyramid. The corner-sharing octahedral tilt angles are 38°. In the second Se2- site, Se2- is bonded to six U4+ atoms to form SeU6 octahedra that share corners with four equivalent SeU3Mn tetrahedra and corners with four equivalent SeU4 trigonal pyramids. In the third Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four U4+ atoms. In the fourth Se2- site, Se2- is bonded to three U4+ and one Mn2+ atom to form distorted SeU3Mn tetrahedra that share a cornercorner with one SeU6 octahedra, corners with five equivalent SeU3Mn tetrahedra, corners with three equivalent SeU4 trigonal pyramids, edges with two equivalent SeU3Mn tetrahedra, and an edgeedge with one SeU4 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. In the fifth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four U4+ atoms. In the sixth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three U4+ and one Mn2+ atom. In the seventh Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four U4+ atoms.