The compound described by 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. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sr2U2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.064
_cell_length_b   6.714
_cell_length_c   6.940
_cell_angle_alpha   69.994
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   177.942
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Sr  Sr0  1  0.000  0.512  0.498  1.0
  Sr  Sr1  1  0.500  0.505  0.995  1.0
  U  U2  1  0.000  0.004  0.011  1.0
  U  U3  1  0.500  0.995  0.485  1.0
  O  O4  1  0.500  0.319  0.392  1.0
  O  O5  1  0.000  0.322  0.889  1.0
  O  O6  1  0.500  0.670  0.598  1.0
  O  O7  1  0.000  0.685  0.111  1.0
  O  O8  1  0.500  0.046  0.150  1.0
  O  O9  1  0.000  0.954  0.405  1.0
  O  O10  1  0.500  0.969  0.807  1.0
[/CIF]
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The compound described by 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. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sr2U2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.064
_cell_length_b   6.714
_cell_length_c   6.940
_cell_angle_alpha   69.994
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   177.942
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Sr  Sr0  1  0.000  0.512  0.498  1.0
  Sr  Sr1  1  0.500  0.505  0.995  1.0
  U  U2  1  0.000  0.004  0.011  1.0
  U  U3  1  0.500  0.995  0.485  1.0
  O  O4  1  0.500  0.319  0.392  1.0
  O  O5  1  0.000  0.322  0.889  1.0
  O  O6  1  0.500  0.670  0.598  1.0
  O  O7  1  0.000  0.685  0.111  1.0
  O  O8  1  0.500  0.046  0.150  1.0
  O  O9  1  0.000  0.954  0.405  1.0
  O  O10  1  0.500  0.969  0.807  1.0
[/CIF]
.