UO3 crystallizes in the monoclinic P2_1 space group. There are five inequivalent U sites. In the first U site, U(1) is bonded to one O(1), one O(2), one O(5), one O(9), and two equivalent O(14) atoms to form corner-sharing UO6 octahedra. The corner-sharing octahedral tilt angles are 30°. In the second U site, U(2) is bonded in a 2-coordinate geometry to one O(12), one O(15), one O(4), one O(7), one O(8), and one O(9) atom. In the third U site, U(3) is bonded in a 7-coordinate geometry to one O(10), one O(15), one O(8), two equivalent O(11), and two equivalent O(5) atoms. In the fourth U site, U(4) is bonded in a 7-coordinate geometry to one O(14), one O(3), one O(6), two equivalent O(1), and two equivalent O(13) atoms. In the fifth U site, U(5) is bonded in a 6-coordinate geometry to one O(11), one O(13), one O(2), one O(7), and two equivalent O(10) atoms. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one U(1) and two equivalent U(4) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one U(1) and one U(5) atom. In the third O site, O(3) is bonded in a single-bond geometry to one U(4) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one U(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one U(1) and two equivalent U(3) atoms. In the sixth O site, O(6) is bonded in a single-bond geometry to one U(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one U(2) and one U(5) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one U(2) and one U(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one U(1) and one U(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one U(3) and two equivalent U(5) atoms. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one U(5) and two equivalent U(3) atoms. In the twelfth O site, O(12) is bonded in a single-bond geometry to one U(2) atom. In the thirteenth O site, O(13) is bonded in a distorted trigonal planar geometry to one U(5) and two equivalent U(4) atoms. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one U(4) and two equivalent U(1) atoms. In the fifteenth O site, O(15) is bonded in a distorted single-bond geometry to one U(2) and one U(3) atom.
UO3 crystallizes in the monoclinic P2_1 space group. There are five inequivalent U sites. In the first U site, U(1) is bonded to one O(1), one O(2), one O(5), one O(9), and two equivalent O(14) atoms to form corner-sharing UO6 octahedra. The corner-sharing octahedral tilt angles are 30°. The U(1)-O(1) bond length is 2.14 Å. The U(1)-O(2) bond length is 2.04 Å. The U(1)-O(5) bond length is 2.04 Å. The U(1)-O(9) bond length is 2.03 Å. Both U(1)-O(14) bond lengths are 2.11 Å. In the second U site, U(2) is bonded in a 2-coordinate geometry to one O(12), one O(15), one O(4), one O(7), one O(8), and one O(9) atom. The U(2)-O(12) bond length is 1.80 Å. The U(2)-O(15) bond length is 2.58 Å. The U(2)-O(4) bond length is 1.82 Å. The U(2)-O(7) bond length is 2.42 Å. The U(2)-O(8) bond length is 2.50 Å. The U(2)-O(9) bond length is 2.20 Å. In the third U site, U(3) is bonded in a 7-coordinate geometry to one O(10), one O(15), one O(8), two equivalent O(11), and two equivalent O(5) atoms. The U(3)-O(10) bond length is 2.47 Å. The U(3)-O(15) bond length is 1.85 Å. The U(3)-O(8) bond length is 1.85 Å. There is one shorter (2.24 Å) and one longer (2.31 Å) U(3)-O(11) bond length. There is one shorter (2.44 Å) and one longer (2.63 Å) U(3)-O(5) bond length. In the fourth U site, U(4) is bonded in a 7-coordinate geometry to one O(14), one O(3), one O(6), two equivalent O(1), and two equivalent O(13) atoms. The U(4)-O(14) bond length is 2.65 Å. The U(4)-O(3) bond length is 1.79 Å. The U(4)-O(6) bond length is 1.80 Å. There is one shorter (2.29 Å) and one longer (2.30 Å) U(4)-O(1) bond length. There is one shorter (2.53 Å) and one longer (2.63 Å) U(4)-O(13) bond length. In the fifth U site, U(5) is bonded in a 6-coordinate geometry to one O(11), one O(13), one O(2), one O(7), and two equivalent O(10) atoms. The U(5)-O(11) bond length is 2.19 Å. The U(5)-O(13) bond length is 1.95 Å. The U(5)-O(2) bond length is 2.36 Å. The U(5)-O(7) bond length is 1.88 Å. There is one shorter (2.19 Å) and one longer (2.20 Å) U(5)-O(10) bond length. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one U(1) and two equivalent U(4) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one U(1) and one U(5) atom. In the third O site, O(3) is bonded in a single-bond geometry to one U(4) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one U(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one U(1) and two equivalent U(3) atoms. In the sixth O site, O(6) is bonded in a single-bond geometry to one U(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one U(2) and one U(5) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one U(2) and one U(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one U(1) and one U(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one U(3) and two equivalent U(5) atoms. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one U(5) and two equivalent U(3) atoms. In the twelfth O site, O(12) is bonded in a single-bond geometry to one U(2) atom. In the thirteenth O site, O(13) is bonded in a distorted trigonal planar geometry to one U(5) and two equivalent U(4) atoms. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one U(4) and two equivalent U(1) atoms. In the fifteenth O site, O(15) is bonded in a distorted single-bond geometry to one U(2) and one U(3) atom.