U3P2Se is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to four equivalent P(1) and two equivalent Se(1) atoms to form a mixture of edge and corner-sharing UP4Se2 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second U site, U(2) is bonded to four equivalent P(1) and two equivalent Se(1) atoms to form a mixture of edge and corner-sharing UP4Se2 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. P(1) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form PU6 octahedra that share corners with two equivalent Se(1)U6 octahedra, corners with four equivalent P(1)U6 octahedra, edges with five equivalent Se(1)U6 octahedra, and edges with seven equivalent P(1)U6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. Se(1) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form SeU6 octahedra that share corners with two equivalent Se(1)U6 octahedra, corners with four equivalent P(1)U6 octahedra, edges with two equivalent Se(1)U6 octahedra, and edges with ten equivalent P(1)U6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°.
U3P2Se is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to four equivalent P(1) and two equivalent Se(1) atoms to form a mixture of edge and corner-sharing UP4Se2 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. All U(1)-P(1) bond lengths are 2.87 Å. Both U(1)-Se(1) bond lengths are 2.89 Å. In the second U site, U(2) is bonded to four equivalent P(1) and two equivalent Se(1) atoms to form a mixture of edge and corner-sharing UP4Se2 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. There are two shorter (2.84 Å) and two longer (2.89 Å) U(2)-P(1) bond lengths. Both U(2)-Se(1) bond lengths are 2.98 Å. P(1) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form PU6 octahedra that share corners with two equivalent Se(1)U6 octahedra, corners with four equivalent P(1)U6 octahedra, edges with five equivalent Se(1)U6 octahedra, and edges with seven equivalent P(1)U6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. Se(1) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form SeU6 octahedra that share corners with two equivalent Se(1)U6 octahedra, corners with four equivalent P(1)U6 octahedra, edges with two equivalent Se(1)U6 octahedra, and edges with ten equivalent P(1)U6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°.