Sr2U2O7 crystallizes in the monoclinic Pm space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one O(2), one O(4), one O(6), two equivalent O(1), and two equivalent O(3) atoms. In the second Sr site, Sr(2) is bonded in a distorted body-centered cubic geometry to one O(1), one O(3), one O(5), one O(7), two equivalent O(2), and two equivalent O(4) atoms. 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 corner-sharing UO6 octahedra. The corner-sharing octahedral tilt angles are 38°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Sr(2), two equivalent Sr(1), and one U(2) atom to form distorted OSr3U tetrahedra that share corners with two equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(3)Sr3U tetrahedra, corners with two equivalent O(7)SrU3 trigonal pyramids, corners with four equivalent O(6)SrU3 trigonal pyramids,  an edgeedge with one O(3)Sr3U tetrahedra, edges with two equivalent O(4)Sr3U tetrahedra, and  an edgeedge with one O(5)SrU3 trigonal pyramid. In the second O site, O(2) is bonded to one Sr(1), two equivalent Sr(2), and one U(1) atom to form distorted OSr3U tetrahedra that share corners with two equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(4)Sr3U tetrahedra, corners with two equivalent O(6)SrU3 trigonal pyramids, corners with four equivalent O(7)SrU3 trigonal pyramids,  an edgeedge with one O(4)Sr3U tetrahedra, edges with two equivalent O(3)Sr3U tetrahedra, and edges with two equivalent O(5)SrU3 trigonal pyramids. In the third O site, O(3) is bonded to one Sr(2), two equivalent Sr(1), and one U(2) atom to form OSr3U tetrahedra that share corners with two equivalent O(3)Sr3U tetrahedra, corners with four equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(4)Sr3U tetrahedra, corners with two equivalent O(5)SrU3 trigonal pyramids,  an edgeedge with one O(1)Sr3U tetrahedra, edges with two equivalent O(2)Sr3U tetrahedra,  an edgeedge with one O(7)SrU3 trigonal pyramid, and edges with two equivalent O(6)SrU3 trigonal pyramids. In the fourth O site, O(4) is bonded to one Sr(1), two equivalent Sr(2), and one U(1) atom to form distorted OSr3U tetrahedra that share corners with two equivalent O(4)Sr3U tetrahedra, corners with four equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(3)Sr3U tetrahedra, corners with four equivalent O(5)SrU3 trigonal pyramids,  an edgeedge with one O(2)Sr3U tetrahedra, edges with two equivalent O(1)Sr3U tetrahedra,  an edgeedge with one O(6)SrU3 trigonal pyramid, and edges with two equivalent O(7)SrU3 trigonal pyramids. In the fifth O site, O(5) is bonded to one Sr(2), one U(2), and two equivalent U(1) atoms to form distorted OSrU3 trigonal pyramids that share corners with two equivalent O(3)Sr3U tetrahedra, corners with four equivalent O(4)Sr3U tetrahedra, corners with two equivalent O(5)SrU3 trigonal pyramids, corners with four equivalent O(7)SrU3 trigonal pyramids,  an edgeedge with one O(1)Sr3U tetrahedra, edges with two equivalent O(2)Sr3U tetrahedra,  an edgeedge with one O(7)SrU3 trigonal pyramid, and edges with two equivalent O(6)SrU3 trigonal pyramids. In the sixth O site, O(6) is bonded to one Sr(1), one U(1), and two equivalent U(2) atoms to form distorted OSrU3 trigonal pyramids that share corners with two equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(1)Sr3U tetrahedra, corners with two equivalent O(6)SrU3 trigonal pyramids, corners with four equivalent O(7)SrU3 trigonal pyramids,  an edgeedge with one O(4)Sr3U tetrahedra, edges with two equivalent O(3)Sr3U tetrahedra, and edges with two equivalent O(5)SrU3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Sr(2), one U(2), and two equivalent U(1) atoms to form distorted OSrU3 trigonal pyramids that share corners with two equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(2)Sr3U tetrahedra, corners with two equivalent O(7)SrU3 trigonal pyramids, corners with four equivalent O(5)SrU3 trigonal pyramids, corners with four equivalent O(6)SrU3 trigonal pyramids,  an edgeedge with one O(3)Sr3U tetrahedra, edges with two equivalent O(4)Sr3U tetrahedra, and  an edgeedge with one O(5)SrU3 trigonal pyramid.
Sr2U2O7 crystallizes in the monoclinic Pm space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one O(2), one O(4), one O(6), two equivalent O(1), and two equivalent O(3) atoms. The Sr(1)-O(2) bond length is 2.58 Å. The Sr(1)-O(4) bond length is 2.54 Å. The Sr(1)-O(6) bond length is 2.81 Å. Both Sr(1)-O(1) bond lengths are 2.65 Å. Both Sr(1)-O(3) bond lengths are 2.50 Å. In the second Sr site, Sr(2) is bonded in a distorted body-centered cubic geometry to one O(1), one O(3), one O(5), one O(7), two equivalent O(2), and two equivalent O(4) atoms. The Sr(2)-O(1) bond length is 2.61 Å. The Sr(2)-O(3) bond length is 2.59 Å. The Sr(2)-O(5) bond length is 2.89 Å. The Sr(2)-O(7) bond length is 2.94 Å. Both Sr(2)-O(2) bond lengths are 2.61 Å. Both Sr(2)-O(4) bond lengths are 2.63 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 2.01 Å. The U(1)-O(4) bond length is 2.01 Å. The U(1)-O(6) bond length is 2.63 Å. Both U(1)-O(5) bond lengths are 2.31 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 corner-sharing UO6 octahedra. The corner-sharing octahedral tilt angles are 38°. The U(2)-O(1) bond length is 2.04 Å. The U(2)-O(3) bond length is 2.05 Å. The U(2)-O(5) bond length is 2.23 Å. The U(2)-O(7) bond length is 2.18 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 to one Sr(2), two equivalent Sr(1), and one U(2) atom to form distorted OSr3U tetrahedra that share corners with two equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(3)Sr3U tetrahedra, corners with two equivalent O(7)SrU3 trigonal pyramids, corners with four equivalent O(6)SrU3 trigonal pyramids,  an edgeedge with one O(3)Sr3U tetrahedra, edges with two equivalent O(4)Sr3U tetrahedra, and  an edgeedge with one O(5)SrU3 trigonal pyramid. In the second O site, O(2) is bonded to one Sr(1), two equivalent Sr(2), and one U(1) atom to form distorted OSr3U tetrahedra that share corners with two equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(4)Sr3U tetrahedra, corners with two equivalent O(6)SrU3 trigonal pyramids, corners with four equivalent O(7)SrU3 trigonal pyramids,  an edgeedge with one O(4)Sr3U tetrahedra, edges with two equivalent O(3)Sr3U tetrahedra, and edges with two equivalent O(5)SrU3 trigonal pyramids. In the third O site, O(3) is bonded to one Sr(2), two equivalent Sr(1), and one U(2) atom to form OSr3U tetrahedra that share corners with two equivalent O(3)Sr3U tetrahedra, corners with four equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(4)Sr3U tetrahedra, corners with two equivalent O(5)SrU3 trigonal pyramids,  an edgeedge with one O(1)Sr3U tetrahedra, edges with two equivalent O(2)Sr3U tetrahedra,  an edgeedge with one O(7)SrU3 trigonal pyramid, and edges with two equivalent O(6)SrU3 trigonal pyramids. In the fourth O site, O(4) is bonded to one Sr(1), two equivalent Sr(2), and one U(1) atom to form distorted OSr3U tetrahedra that share corners with two equivalent O(4)Sr3U tetrahedra, corners with four equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(3)Sr3U tetrahedra, corners with four equivalent O(5)SrU3 trigonal pyramids,  an edgeedge with one O(2)Sr3U tetrahedra, edges with two equivalent O(1)Sr3U tetrahedra,  an edgeedge with one O(6)SrU3 trigonal pyramid, and edges with two equivalent O(7)SrU3 trigonal pyramids. In the fifth O site, O(5) is bonded to one Sr(2), one U(2), and two equivalent U(1) atoms to form distorted OSrU3 trigonal pyramids that share corners with two equivalent O(3)Sr3U tetrahedra, corners with four equivalent O(4)Sr3U tetrahedra, corners with two equivalent O(5)SrU3 trigonal pyramids, corners with four equivalent O(7)SrU3 trigonal pyramids,  an edgeedge with one O(1)Sr3U tetrahedra, edges with two equivalent O(2)Sr3U tetrahedra,  an edgeedge with one O(7)SrU3 trigonal pyramid, and edges with two equivalent O(6)SrU3 trigonal pyramids. In the sixth O site, O(6) is bonded to one Sr(1), one U(1), and two equivalent U(2) atoms to form distorted OSrU3 trigonal pyramids that share corners with two equivalent O(2)Sr3U tetrahedra, corners with four equivalent O(1)Sr3U tetrahedra, corners with two equivalent O(6)SrU3 trigonal pyramids, corners with four equivalent O(7)SrU3 trigonal pyramids,  an edgeedge with one O(4)Sr3U tetrahedra, edges with two equivalent O(3)Sr3U tetrahedra, and edges with two equivalent O(5)SrU3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Sr(2), one U(2), and two equivalent U(1) atoms to form distorted OSrU3 trigonal pyramids that share corners with two equivalent O(1)Sr3U tetrahedra, corners with four equivalent O(2)Sr3U tetrahedra, corners with two equivalent O(7)SrU3 trigonal pyramids, corners with four equivalent O(5)SrU3 trigonal pyramids, corners with four equivalent O(6)SrU3 trigonal pyramids,  an edgeedge with one O(3)Sr3U tetrahedra, edges with two equivalent O(4)Sr3U tetrahedra, and  an edgeedge with one O(5)SrU3 trigonal pyramid.