UNiSe3 crystallizes in the orthorhombic Pnma space group. U(1) is bonded in a 8-coordinate geometry to two equivalent Se(1) and six equivalent Se(2) atoms. Ni(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form corner-sharing NiSe6 octahedra. The corner-sharing octahedral tilt angles range from 41-48°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent U(1) and two equivalent Ni(1) atoms to form distorted corner-sharing SeU2Ni2 trigonal pyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to three equivalent U(1) and two equivalent Ni(1) atoms.
UNiSe3 crystallizes in the orthorhombic Pnma space group. U(1) is bonded in a 8-coordinate geometry to two equivalent Se(1) and six equivalent Se(2) atoms. There is one shorter (2.79 Å) and one longer (2.89 Å) U(1)-Se(1) bond length. There are a spread of U(1)-Se(2) bond distances ranging from 2.83-3.05 Å. Ni(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form corner-sharing NiSe6 octahedra. The corner-sharing octahedral tilt angles range from 41-48°. Both Ni(1)-Se(1) bond lengths are 2.42 Å. There are two shorter (2.49 Å) and two longer (2.67 Å) Ni(1)-Se(2) bond lengths. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent U(1) and two equivalent Ni(1) atoms to form distorted corner-sharing SeU2Ni2 trigonal pyramids. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to three equivalent U(1) and two equivalent Ni(1) atoms.