U3O7 crystallizes in the orthorhombic Immm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(3), four equivalent O(1), and four equivalent O(2) atoms. In the second U site, U(2) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(3), and six equivalent O(2) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent U(1) and two equivalent U(2) atoms to form OU4 tetrahedra that share corners with two equivalent O(3)U6 octahedra, corners with four equivalent O(1)U4 tetrahedra, corners with twelve equivalent O(2)U4 tetrahedra, edges with two equivalent O(1)U4 tetrahedra, edges with four equivalent O(2)U4 tetrahedra, and faces with two equivalent O(3)U6 octahedra. The corner-sharing octahedral tilt angles are 58°. In the second O site, O(2) is bonded to one U(1) and three equivalent U(2) atoms to form OU4 tetrahedra that share corners with five equivalent O(3)U6 octahedra, corners with six equivalent O(1)U4 tetrahedra, corners with ten equivalent O(2)U4 tetrahedra, edges with two equivalent O(1)U4 tetrahedra, edges with four equivalent O(2)U4 tetrahedra, and  a faceface with one O(3)U6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. In the third O site, O(3) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form OU6 octahedra that share corners with two equivalent O(3)U6 octahedra, corners with four equivalent O(1)U4 tetrahedra, corners with twenty equivalent O(2)U4 tetrahedra, edges with two equivalent O(3)U6 octahedra, faces with four equivalent O(1)U4 tetrahedra, and faces with four equivalent O(2)U4 tetrahedra. The corner-sharing octahedra are not tilted.
U3O7 crystallizes in the orthorhombic Immm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(3), four equivalent O(1), and four equivalent O(2) atoms. Both U(1)-O(3) bond lengths are 2.75 Å. All U(1)-O(1) bond lengths are 2.24 Å. All U(1)-O(2) bond lengths are 2.38 Å. In the second U site, U(2) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(3), and six equivalent O(2) atoms. Both U(2)-O(1) bond lengths are 2.34 Å. Both U(2)-O(3) bond lengths are 2.58 Å. There are two shorter (2.30 Å) and four longer (2.40 Å) U(2)-O(2) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent U(1) and two equivalent U(2) atoms to form OU4 tetrahedra that share corners with two equivalent O(3)U6 octahedra, corners with four equivalent O(1)U4 tetrahedra, corners with twelve equivalent O(2)U4 tetrahedra, edges with two equivalent O(1)U4 tetrahedra, edges with four equivalent O(2)U4 tetrahedra, and faces with two equivalent O(3)U6 octahedra. The corner-sharing octahedral tilt angles are 58°. In the second O site, O(2) is bonded to one U(1) and three equivalent U(2) atoms to form OU4 tetrahedra that share corners with five equivalent O(3)U6 octahedra, corners with six equivalent O(1)U4 tetrahedra, corners with ten equivalent O(2)U4 tetrahedra, edges with two equivalent O(1)U4 tetrahedra, edges with four equivalent O(2)U4 tetrahedra, and  a faceface with one O(3)U6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. In the third O site, O(3) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form OU6 octahedra that share corners with two equivalent O(3)U6 octahedra, corners with four equivalent O(1)U4 tetrahedra, corners with twenty equivalent O(2)U4 tetrahedra, edges with two equivalent O(3)U6 octahedra, faces with four equivalent O(1)U4 tetrahedra, and faces with four equivalent O(2)U4 tetrahedra. The corner-sharing octahedra are not tilted.