UO3 crystallizes in the orthorhombic Fddd space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second U site, U(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form edge-sharing UO6 octahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one U(1) and one U(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one U(1) and two equivalent U(2) atoms. In the third O site, O(3) is bonded in a single-bond geometry to one U(1) atom.
UO3 crystallizes in the orthorhombic Fddd space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both U(1)-O(1) bond lengths are 2.35 Å. Both U(1)-O(2) bond lengths are 2.35 Å. Both U(1)-O(3) bond lengths are 1.82 Å. In the second U site, U(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form edge-sharing UO6 octahedra. Both U(2)-O(1) bond lengths are 1.91 Å. There are two shorter (2.22 Å) and two longer (2.24 Å) U(2)-O(2) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one U(1) and one U(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one U(1) and two equivalent U(2) atoms. In the third O site, O(3) is bonded in a single-bond geometry to one U(1) atom.