DOE OSTI2020
U5P3Se2 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent U sites. In the first U site, U is bonded to three P and three Se atoms to form a mixture of edge and corner-sharing UP3Se3 octahedra. The corner-sharing octahedra tilt angles range from 2–3°. There are a spread of U–P bond distances ranging from 2.76–2.82 Å. There are two shorter (2.84 Å) and one longer (2.86 Å) U–Se bond lengths. In the second U site, U is bonded to four P and two equivalent Se atoms to form a mixture of edge and corner-sharing UP4Se2 octahedra. The corner-sharing octahedra tilt angles range from 2–4°. There are a spread of U–P bond distances ranging from 2.75–2.81 Å. There are one shorter (2.87 Å) and one longer (2.88 Å) U–Se bond lengths. In the third U site, U is bonded to four P and two equivalent Se atoms to form UP4Se2 octahedra that share corners with six UP4Se2 octahedra and edges with twelve UP3Se3 octahedra. The corner-sharing octahedra tilt angles range from 1–2°. There are two shorter (2.79 Å) and two longer (2.81 Å) U–P bond lengths. Both U–Se bond lengths are 2.81 Å. There are three inequivalent P sites. In the first P site, P is bonded to six U atoms to form PU6 octahedra that share corners with six PU6 octahedra, edges with five PU6 octahedra, and edges with seven SeU6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the second P site, P is bonded to six U atoms to form PU6 octahedra that share corners with two equivalent PU6 octahedra, corners with four SeU6 octahedra, edges with five SeU6 octahedra, and edges with seven PU6 octahedra. The corner-sharing octahedra tilt angles range from 1–4°. In the third P site, P is bonded to six U atoms to form PU6 octahedra that share corners with two equivalent SeU6 octahedra, corners with four PU6 octahedra, edges with six PU6 octahedra, and edges with six SeU6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are two inequivalent Se sites. In the first Se site, Se is bonded to six U atoms to form SeU6 octahedra that share corners with two equivalent PU6 octahedra, corners with four SeU6 octahedra, edges with three SeU6 octahedra, and edges with nine PU6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the second Se site, Se is bonded to six U atoms to form SeU6 octahedra that share corners with two equivalent SeU6 octahedra, corners with four PU6 octahedra, edges with three SeU6 octahedra, and edges with nine PU6 octahedra. The corner-sharing octahedra tilt angles range from 3–4°.