Rb2U2O7 crystallizes in the monoclinic Pm space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form RbO6 octahedra that share corners with four equivalent U(2)O6 octahedra, edges with two equivalent Rb(1)O6 octahedra, and edges with four equivalent Rb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. In the second Rb site, Rb(2) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form RbO6 octahedra that share corners with two equivalent U(2)O6 octahedra, edges with two equivalent Rb(2)O6 octahedra, and edges with four equivalent Rb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 57°. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 7-coordinate geometry to one O(2), one O(4), one O(6), two equivalent O(5), and two equivalent O(7) atoms. In the second U site, U(2) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(6) atoms to form distorted UO6 octahedra that share corners with two equivalent Rb(2)O6 octahedra, corners with two equivalent U(2)O6 octahedra, and corners with four equivalent Rb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-57°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Rb(2), two equivalent Rb(1), and one U(2) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Rb(1), two equivalent Rb(2), and one U(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Rb(2), two equivalent Rb(1), and one U(2) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Rb(1), two equivalent Rb(2), and one U(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one U(1) and two equivalent U(2) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one U(2) and two equivalent U(1) atoms.
Rb2U2O7 crystallizes in the monoclinic Pm space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form RbO6 octahedra that share corners with four equivalent U(2)O6 octahedra, edges with two equivalent Rb(1)O6 octahedra, and edges with four equivalent Rb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. The Rb(1)-O(2) bond length is 2.88 Å. The Rb(1)-O(4) bond length is 2.82 Å. Both Rb(1)-O(1) bond lengths are 2.89 Å. Both Rb(1)-O(3) bond lengths are 2.81 Å. In the second Rb site, Rb(2) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form RbO6 octahedra that share corners with two equivalent U(2)O6 octahedra, edges with two equivalent Rb(2)O6 octahedra, and edges with four equivalent Rb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 57°. The Rb(2)-O(1) bond length is 2.94 Å. The Rb(2)-O(3) bond length is 2.91 Å. Both Rb(2)-O(2) bond lengths are 2.91 Å. Both Rb(2)-O(4) bond lengths are 2.93 Å. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 7-coordinate geometry to one O(2), one O(4), one O(6), two equivalent O(5), and two equivalent O(7) atoms. The U(1)-O(2) bond length is 1.87 Å. The U(1)-O(4) bond length is 1.86 Å. The U(1)-O(6) bond length is 2.54 Å. Both U(1)-O(5) bond lengths are 2.26 Å. Both U(1)-O(7) bond lengths are 2.56 Å. In the second U site, U(2) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(6) atoms to form distorted UO6 octahedra that share corners with two equivalent Rb(2)O6 octahedra, corners with two equivalent U(2)O6 octahedra, and corners with four equivalent Rb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-57°. The U(2)-O(1) bond length is 1.91 Å. The U(2)-O(3) bond length is 1.91 Å. The U(2)-O(5) bond length is 2.30 Å. The U(2)-O(7) bond length is 2.20 Å. Both U(2)-O(6) bond lengths are 2.16 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Rb(2), two equivalent Rb(1), and one U(2) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Rb(1), two equivalent Rb(2), and one U(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Rb(2), two equivalent Rb(1), and one U(2) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Rb(1), two equivalent Rb(2), and one U(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one U(1) and two equivalent U(2) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one U(2) and two equivalent U(1) atoms.