The material structure described by Na2U2O7 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(6), one O(7), two equivalent O(4), and two equivalent O(5) atoms. In the second Na site, Na(2) is bonded to one O(1), one O(4), one O(5), two equivalent O(3), and two equivalent O(6) atoms to form distorted NaO7 pentagonal bipyramids that share corners with two equivalent U(1)O6 octahedra,  a cornercorner with one U(2)O7 pentagonal bipyramid, edges with two equivalent U(1)O6 octahedra,  an edgeedge with one U(2)O7 pentagonal bipyramid, and edges with two equivalent Na(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 55-56°. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(2), one O(3), one O(6), one O(7), and two equivalent O(1) atoms to form UO6 octahedra that share corners with two equivalent U(1)O6 octahedra, corners with two equivalent Na(2)O7 pentagonal bipyramids, corners with two equivalent U(2)O7 pentagonal bipyramids, edges with two equivalent Na(2)O7 pentagonal bipyramids, and edges with two equivalent U(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 51°. In the second U site, U(2) is bonded to one O(1), one O(4), one O(5), two equivalent O(2), and two equivalent O(7) atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(1)O6 octahedra,  a cornercorner with one Na(2)O7 pentagonal bipyramid, edges with two equivalent U(1)O6 octahedra,  an edgeedge with one Na(2)O7 pentagonal bipyramid, and edges with two equivalent U(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 37-39°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), one U(2), and two equivalent U(1) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(2)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the second O site, O(2) is bonded to one Na(1), one U(1), and two equivalent U(2) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with four equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the third O site, O(3) is bonded to one Na(1), two equivalent Na(2), and one U(1) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with four equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Na(2), two equivalent Na(1), and one U(2) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with four equivalent O(5)Na3U tetrahedra, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid,  an edgeedge with one O(2)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Na(2), two equivalent Na(1), and one U(2) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with four equivalent O(4)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(2)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the sixth O site, O(6) is bonded to one Na(1), two equivalent Na(2), and one U(1) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with four equivalent O(3)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(2)NaU3 trigonal pyramid. In the seventh O site, O(7) is bonded to one Na(1), one U(1), and two equivalent U(2) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids, corners with four equivalent O(2)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(2)NaU3 trigonal pyramid. is represented by the CIF card [CIF]
data_Na2U2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.387
_cell_length_b   6.872
_cell_length_c   7.814
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   111.099
_symmetry_Int_Tables_number   1
_cell_volume   319.950
_cell_formula_units_Z   2
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
  Na  Na0  1  0.500  0.500  0.497  1.0
  Na  Na1  1  0.500  0.500  0.997  1.0
  Na  Na2  1  0.514  0.992  0.247  1.0
  Na  Na3  1  0.486  0.008  0.747  1.0
  U  U4  1  0.000  0.999  0.998  1.0
  U  U5  1  1.000  0.001  0.498  1.0
  U  U6  1  0.005  0.536  0.748  1.0
  U  U7  1  0.995  0.464  0.248  1.0
  O  O8  1  0.052  0.888  0.748  1.0
  O  O9  1  0.948  0.112  0.248  1.0
  O  O10  1  0.980  0.677  0.041  1.0
  O  O11  1  0.020  0.323  0.541  1.0
  O  O12  1  0.686  0.900  0.523  1.0
  O  O13  1  0.314  0.100  0.023  1.0
  O  O14  1  0.315  0.633  0.748  1.0
  O  O15  1  0.685  0.367  0.248  1.0
  O  O16  1  0.692  0.428  0.747  1.0
  O  O17  1  0.308  0.572  0.247  1.0
  O  O18  1  0.686  0.897  0.973  1.0
  O  O19  1  0.314  0.103  0.473  1.0
  O  O20  1  0.980  0.681  0.451  1.0
  O  O21  1  0.020  0.319  0.951  1.0
[/CIF]
.
The material structure described by Na2U2O7 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(6), one O(7), two equivalent O(4), and two equivalent O(5) atoms. In the second Na site, Na(2) is bonded to one O(1), one O(4), one O(5), two equivalent O(3), and two equivalent O(6) atoms to form distorted NaO7 pentagonal bipyramids that share corners with two equivalent U(1)O6 octahedra,  a cornercorner with one U(2)O7 pentagonal bipyramid, edges with two equivalent U(1)O6 octahedra,  an edgeedge with one U(2)O7 pentagonal bipyramid, and edges with two equivalent Na(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 55-56°. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(2), one O(3), one O(6), one O(7), and two equivalent O(1) atoms to form UO6 octahedra that share corners with two equivalent U(1)O6 octahedra, corners with two equivalent Na(2)O7 pentagonal bipyramids, corners with two equivalent U(2)O7 pentagonal bipyramids, edges with two equivalent Na(2)O7 pentagonal bipyramids, and edges with two equivalent U(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 51°. In the second U site, U(2) is bonded to one O(1), one O(4), one O(5), two equivalent O(2), and two equivalent O(7) atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(1)O6 octahedra,  a cornercorner with one Na(2)O7 pentagonal bipyramid, edges with two equivalent U(1)O6 octahedra,  an edgeedge with one Na(2)O7 pentagonal bipyramid, and edges with two equivalent U(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 37-39°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), one U(2), and two equivalent U(1) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(2)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the second O site, O(2) is bonded to one Na(1), one U(1), and two equivalent U(2) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with four equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the third O site, O(3) is bonded to one Na(1), two equivalent Na(2), and one U(1) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with four equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Na(2), two equivalent Na(1), and one U(2) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with four equivalent O(5)Na3U tetrahedra, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid,  an edgeedge with one O(2)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Na(2), two equivalent Na(1), and one U(2) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(3)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with four equivalent O(4)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(2)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(2)NaU3 trigonal pyramid, and  an edgeedge with one O(7)NaU3 trigonal pyramid. In the sixth O site, O(6) is bonded to one Na(1), two equivalent Na(2), and one U(1) atom to form distorted ONa3U tetrahedra that share corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with four equivalent O(3)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(2)NaU3 trigonal pyramid. In the seventh O site, O(7) is bonded to one Na(1), one U(1), and two equivalent U(2) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(4)Na3U tetrahedra, corners with two equivalent O(5)Na3U tetrahedra, corners with two equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(7)NaU3 trigonal pyramids, corners with four equivalent O(2)NaU3 trigonal pyramids,  an edgeedge with one O(3)Na3U tetrahedra,  an edgeedge with one O(4)Na3U tetrahedra,  an edgeedge with one O(5)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(2)NaU3 trigonal pyramid. is represented by the CIF card [CIF]
data_Na2U2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.387
_cell_length_b   6.872
_cell_length_c   7.814
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   111.099
_symmetry_Int_Tables_number   1
_cell_volume   319.950
_cell_formula_units_Z   2
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
  Na  Na0  1  0.500  0.500  0.497  1.0
  Na  Na1  1  0.500  0.500  0.997  1.0
  Na  Na2  1  0.514  0.992  0.247  1.0
  Na  Na3  1  0.486  0.008  0.747  1.0
  U  U4  1  0.000  0.999  0.998  1.0
  U  U5  1  1.000  0.001  0.498  1.0
  U  U6  1  0.005  0.536  0.748  1.0
  U  U7  1  0.995  0.464  0.248  1.0
  O  O8  1  0.052  0.888  0.748  1.0
  O  O9  1  0.948  0.112  0.248  1.0
  O  O10  1  0.980  0.677  0.041  1.0
  O  O11  1  0.020  0.323  0.541  1.0
  O  O12  1  0.686  0.900  0.523  1.0
  O  O13  1  0.314  0.100  0.023  1.0
  O  O14  1  0.315  0.633  0.748  1.0
  O  O15  1  0.685  0.367  0.248  1.0
  O  O16  1  0.692  0.428  0.747  1.0
  O  O17  1  0.308  0.572  0.247  1.0
  O  O18  1  0.686  0.897  0.973  1.0
  O  O19  1  0.314  0.103  0.473  1.0
  O  O20  1  0.980  0.681  0.451  1.0
  O  O21  1  0.020  0.319  0.951  1.0
[/CIF]
.