U2Se3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing USe7 pentagonal bipyramids. In the second U site, U(2) is bonded in a 8-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and three equivalent Se(3) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent U(2) and three equivalent U(1) atoms to form a mixture of corner and edge-sharing SeU5 square pyramids. In the second Se site, Se(2) is bonded to two equivalent U(1) and three equivalent U(2) atoms to form a mixture of distorted corner and edge-sharing SeU5 trigonal bipyramids. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to two equivalent U(1) and three equivalent U(2) atoms.
U2Se3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing USe7 pentagonal bipyramids. Both U(1)-Se(2) bond lengths are 2.93 Å. There is one shorter (2.95 Å) and one longer (3.01 Å) U(1)-Se(3) bond length. There are two shorter (2.91 Å) and one longer (2.94 Å) U(1)-Se(1) bond length. In the second U site, U(2) is bonded in a 8-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and three equivalent Se(3) atoms. Both U(2)-Se(1) bond lengths are 3.03 Å. There are two shorter (3.01 Å) and one longer (3.05 Å) U(2)-Se(2) bond length. There are two shorter (3.02 Å) and one longer (3.49 Å) U(2)-Se(3) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent U(2) and three equivalent U(1) atoms to form a mixture of corner and edge-sharing SeU5 square pyramids. In the second Se site, Se(2) is bonded to two equivalent U(1) and three equivalent U(2) atoms to form a mixture of distorted corner and edge-sharing SeU5 trigonal bipyramids. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to two equivalent U(1) and three equivalent U(2) atoms.