K2U2O7 crystallizes in the monoclinic Pm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form KO6 octahedra that share corners with four equivalent U(2)O6 octahedra, edges with two equivalent K(1)O6 octahedra, and edges with four equivalent K(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-58°. In the second K site, K(2) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form distorted KO6 octahedra that share corners with two equivalent U(2)O6 octahedra, edges with two equivalent K(2)O6 octahedra, and edges with four equivalent K(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. 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 K(2)O6 octahedra, corners with two equivalent U(2)O6 octahedra, and corners with four equivalent K(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-60°. 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 K(2), two equivalent K(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 K(1), two equivalent K(2), and one U(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(2), two equivalent K(1), and one U(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one U(1) atom. In the fifth O site, O(5) is bonded in a distorted 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.
K2U2O7 crystallizes in the monoclinic Pm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form KO6 octahedra that share corners with four equivalent U(2)O6 octahedra, edges with two equivalent K(1)O6 octahedra, and edges with four equivalent K(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-58°. The K(1)-O(2) bond length is 2.78 Å. The K(1)-O(4) bond length is 2.71 Å. Both K(1)-O(1) bond lengths are 2.78 Å. Both K(1)-O(3) bond lengths are 2.71 Å. In the second K site, K(2) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form distorted KO6 octahedra that share corners with two equivalent U(2)O6 octahedra, edges with two equivalent K(2)O6 octahedra, and edges with four equivalent K(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. The K(2)-O(1) bond length is 2.82 Å. The K(2)-O(3) bond length is 2.80 Å. Both K(2)-O(2) bond lengths are 2.81 Å. Both K(2)-O(4) bond lengths are 2.81 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 1.87 Å. The U(1)-O(6) bond length is 2.54 Å. Both U(1)-O(5) bond lengths are 2.25 Å. Both U(1)-O(7) bond lengths are 2.54 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 K(2)O6 octahedra, corners with two equivalent U(2)O6 octahedra, and corners with four equivalent K(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-60°. 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 2.29 Å. The U(2)-O(7) bond length is 2.20 Å. Both U(2)-O(6) bond lengths are 2.15 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 K(2), two equivalent K(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 K(1), two equivalent K(2), and one U(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(2), two equivalent K(1), and one U(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one U(1) atom. In the fifth O site, O(5) is bonded in a distorted 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.