U11Se20 crystallizes in the tetragonal P4 space group. There are five inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one Se(2), one Se(3), one Se(5), one Se(6), two equivalent Se(1), and two equivalent Se(4) atoms. In the second U site, U(2) is bonded in a 8-coordinate geometry to one Se(1), one Se(4), one Se(5), one Se(6), two equivalent Se(2), and two equivalent Se(3) atoms. In the third U site, U(3) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. In the fourth U site, U(4) is bonded in a 8-coordinate geometry to four equivalent Se(3) and four equivalent Se(4) atoms. In the fifth U site, U(5) is bonded in a 8-coordinate geometry to four equivalent Se(3) and four equivalent Se(4) atoms. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one U(2), one U(3), and two equivalent U(1) atoms to form SeU4 trigonal pyramids that share  a cornercorner with one Se(5)U4 tetrahedra, corners with three equivalent Se(6)U4 tetrahedra, corners with two equivalent Se(3)U5 trigonal bipyramids, corners with five equivalent Se(4)U5 trigonal bipyramids,  a cornercorner with one Se(1)U4 trigonal pyramid,  an edgeedge with one Se(5)U4 tetrahedra,  an edgeedge with one Se(3)U5 trigonal bipyramid, and edges with two equivalent Se(1)U4 trigonal pyramids. In the second Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to one U(1), one U(3), and two equivalent U(2) atoms. In the third Se site, Se(3) is bonded to one U(1), one U(4), one U(5), and two equivalent U(2) atoms to form distorted SeU5 trigonal bipyramids that share  a cornercorner with one Se(5)U4 tetrahedra, corners with three equivalent Se(6)U4 tetrahedra, corners with four equivalent Se(4)U5 trigonal bipyramids, corners with two equivalent Se(1)U4 trigonal pyramids,  an edgeedge with one Se(5)U4 tetrahedra,  an edgeedge with one Se(3)U5 trigonal bipyramid, edges with four equivalent Se(4)U5 trigonal bipyramids,  an edgeedge with one Se(1)U4 trigonal pyramid, and faces with two equivalent Se(3)U5 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to one U(2), one U(4), one U(5), and two equivalent U(1) atoms to form distorted SeU5 trigonal bipyramids that share  a cornercorner with one Se(6)U4 tetrahedra, corners with three equivalent Se(5)U4 tetrahedra, corners with four equivalent Se(3)U5 trigonal bipyramids, corners with five equivalent Se(1)U4 trigonal pyramids,  an edgeedge with one Se(6)U4 tetrahedra,  an edgeedge with one Se(4)U5 trigonal bipyramid, edges with four equivalent Se(3)U5 trigonal bipyramids, and faces with two equivalent Se(4)U5 trigonal bipyramids. In the fifth Se site, Se(5) is bonded to two equivalent U(1) and two equivalent U(2) atoms to form SeU4 tetrahedra that share corners with two equivalent Se(3)U5 trigonal bipyramids, corners with six equivalent Se(4)U5 trigonal bipyramids, corners with two equivalent Se(1)U4 trigonal pyramids, edges with two equivalent Se(6)U4 tetrahedra, edges with two equivalent Se(3)U5 trigonal bipyramids, and edges with two equivalent Se(1)U4 trigonal pyramids. In the sixth Se site, Se(6) is bonded to two equivalent U(1) and two equivalent U(2) atoms to form SeU4 tetrahedra that share corners with two equivalent Se(4)U5 trigonal bipyramids, corners with six equivalent Se(3)U5 trigonal bipyramids, corners with six equivalent Se(1)U4 trigonal pyramids, edges with two equivalent Se(5)U4 tetrahedra, and edges with two equivalent Se(4)U5 trigonal bipyramids.
U11Se20 crystallizes in the tetragonal P4 space group. There are five inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one Se(2), one Se(3), one Se(5), one Se(6), two equivalent Se(1), and two equivalent Se(4) atoms. The U(1)-Se(2) bond length is 2.93 Å. The U(1)-Se(3) bond length is 2.99 Å. The U(1)-Se(5) bond length is 2.89 Å. The U(1)-Se(6) bond length is 2.89 Å. There is one shorter (2.90 Å) and one longer (3.05 Å) U(1)-Se(1) bond length. There is one shorter (2.99 Å) and one longer (3.18 Å) U(1)-Se(4) bond length. In the second U site, U(2) is bonded in a 8-coordinate geometry to one Se(1), one Se(4), one Se(5), one Se(6), two equivalent Se(2), and two equivalent Se(3) atoms. The U(2)-Se(1) bond length is 2.91 Å. The U(2)-Se(4) bond length is 2.98 Å. The U(2)-Se(5) bond length is 2.89 Å. The U(2)-Se(6) bond length is 2.89 Å. There is one shorter (2.92 Å) and one longer (3.06 Å) U(2)-Se(2) bond length. There is one shorter (2.99 Å) and one longer (3.16 Å) U(2)-Se(3) bond length. In the third U site, U(3) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. All U(3)-Se(1) bond lengths are 2.97 Å. All U(3)-Se(2) bond lengths are 2.92 Å. In the fourth U site, U(4) is bonded in a 8-coordinate geometry to four equivalent Se(3) and four equivalent Se(4) atoms. All U(4)-Se(3) bond lengths are 2.92 Å. All U(4)-Se(4) bond lengths are 2.99 Å. In the fifth U site, U(5) is bonded in a 8-coordinate geometry to four equivalent Se(3) and four equivalent Se(4) atoms. All U(5)-Se(3) bond lengths are 2.98 Å. All U(5)-Se(4) bond lengths are 2.92 Å. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one U(2), one U(3), and two equivalent U(1) atoms to form SeU4 trigonal pyramids that share  a cornercorner with one Se(5)U4 tetrahedra, corners with three equivalent Se(6)U4 tetrahedra, corners with two equivalent Se(3)U5 trigonal bipyramids, corners with five equivalent Se(4)U5 trigonal bipyramids,  a cornercorner with one Se(1)U4 trigonal pyramid,  an edgeedge with one Se(5)U4 tetrahedra,  an edgeedge with one Se(3)U5 trigonal bipyramid, and edges with two equivalent Se(1)U4 trigonal pyramids. In the second Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to one U(1), one U(3), and two equivalent U(2) atoms. In the third Se site, Se(3) is bonded to one U(1), one U(4), one U(5), and two equivalent U(2) atoms to form distorted SeU5 trigonal bipyramids that share  a cornercorner with one Se(5)U4 tetrahedra, corners with three equivalent Se(6)U4 tetrahedra, corners with four equivalent Se(4)U5 trigonal bipyramids, corners with two equivalent Se(1)U4 trigonal pyramids,  an edgeedge with one Se(5)U4 tetrahedra,  an edgeedge with one Se(3)U5 trigonal bipyramid, edges with four equivalent Se(4)U5 trigonal bipyramids,  an edgeedge with one Se(1)U4 trigonal pyramid, and faces with two equivalent Se(3)U5 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to one U(2), one U(4), one U(5), and two equivalent U(1) atoms to form distorted SeU5 trigonal bipyramids that share  a cornercorner with one Se(6)U4 tetrahedra, corners with three equivalent Se(5)U4 tetrahedra, corners with four equivalent Se(3)U5 trigonal bipyramids, corners with five equivalent Se(1)U4 trigonal pyramids,  an edgeedge with one Se(6)U4 tetrahedra,  an edgeedge with one Se(4)U5 trigonal bipyramid, edges with four equivalent Se(3)U5 trigonal bipyramids, and faces with two equivalent Se(4)U5 trigonal bipyramids. In the fifth Se site, Se(5) is bonded to two equivalent U(1) and two equivalent U(2) atoms to form SeU4 tetrahedra that share corners with two equivalent Se(3)U5 trigonal bipyramids, corners with six equivalent Se(4)U5 trigonal bipyramids, corners with two equivalent Se(1)U4 trigonal pyramids, edges with two equivalent Se(6)U4 tetrahedra, edges with two equivalent Se(3)U5 trigonal bipyramids, and edges with two equivalent Se(1)U4 trigonal pyramids. In the sixth Se site, Se(6) is bonded to two equivalent U(1) and two equivalent U(2) atoms to form SeU4 tetrahedra that share corners with two equivalent Se(4)U5 trigonal bipyramids, corners with six equivalent Se(3)U5 trigonal bipyramids, corners with six equivalent Se(1)U4 trigonal pyramids, edges with two equivalent Se(5)U4 tetrahedra, and edges with two equivalent Se(4)U5 trigonal bipyramids.