The structure described by Na2U2O7 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms to form distorted NaO6 octahedra that share corners with four equivalent U(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-56°. In the third Na site, Na(3) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form UO6 octahedra that share corners with two equivalent Na(2)O6 octahedra and corners with two equivalent U(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-56°. In the second U site, U(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(6), one O(7), and two equivalent O(3) atoms. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Na(3), and one U(1) atom. In the second O site, O(6) is bonded to one Na(1), two equivalent Na(3), and one U(2) atom to form distorted ONa3U tetrahedra that share  a cornercorner with one O(6)Na3U tetrahedra,  a cornercorner with one O(1)NaU3 trigonal pyramid, corners with two equivalent O(3)NaU3 trigonal pyramids,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(3)NaU3 trigonal pyramid. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(3), and one U(2) atom. In the fourth O site, O(1) is bonded to one Na(1), one U(2), and two equivalent U(1) atoms to form distorted ONaU3 trigonal pyramids that share  a cornercorner with one O(6)Na3U tetrahedra, corners with two equivalent O(3)NaU3 trigonal pyramids, corners with three equivalent O(1)NaU3 trigonal pyramids,  an edgeedge with one O(6)Na3U tetrahedra, and  an edgeedge with one O(3)NaU3 trigonal pyramid. In the fifth O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(3), one U(1), and one U(2) atom. In the sixth O site, O(3) is bonded to one Na(3), one U(1), and two equivalent U(2) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(3)NaU3 trigonal pyramids,  an edgeedge with one O(6)Na3U tetrahedra, and  an edgeedge with one O(1)NaU3 trigonal pyramid. In the seventh O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Na(3), and one U(1) atom. is represented by the CIF file [CIF]
data_Na2U2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.928
_cell_length_b   7.920
_cell_length_c   12.453
_cell_angle_alpha   90.000
_cell_angle_beta   79.331
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   671.456
_cell_formula_units_Z   4
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  0.500  1.0
  Na  Na1  1  0.000  0.000  0.000  1.0
  Na  Na2  1  0.000  0.500  0.000  1.0
  Na  Na3  1  0.500  0.000  0.500  1.0
  Na  Na4  1  1.000  0.746  0.506  1.0
  Na  Na5  1  0.500  0.246  0.994  1.0
  Na  Na6  1  0.000  0.254  0.494  1.0
  Na  Na7  1  0.500  0.754  0.006  1.0
  U  U8  1  0.739  0.752  0.252  1.0
  U  U9  1  0.761  0.252  0.248  1.0
  U  U10  1  0.261  0.248  0.748  1.0
  U  U11  1  0.239  0.748  0.752  1.0
  U  U12  1  0.280  0.507  0.256  1.0
  U  U13  1  0.220  0.007  0.244  1.0
  U  U14  1  0.720  0.493  0.744  1.0
  U  U15  1  0.780  0.993  0.756  1.0
  O  O16  1  0.610  0.499  0.270  1.0
  O  O17  1  0.890  0.999  0.230  1.0
  O  O18  1  0.390  0.501  0.730  1.0
  O  O19  1  0.110  0.001  0.770  1.0
  O  O20  1  0.463  0.180  0.238  1.0
  O  O21  1  0.037  0.680  0.262  1.0
  O  O22  1  0.537  0.820  0.762  1.0
  O  O23  1  0.963  0.320  0.738  1.0
  O  O24  1  0.421  0.784  0.241  1.0
  O  O25  1  0.079  0.284  0.259  1.0
  O  O26  1  0.579  0.216  0.759  1.0
  O  O27  1  0.921  0.716  0.741  1.0
  O  O28  1  0.820  0.276  0.094  1.0
  O  O29  1  0.680  0.776  0.406  1.0
  O  O30  1  0.180  0.724  0.906  1.0
  O  O31  1  0.320  0.224  0.594  1.0
  O  O32  1  0.793  0.729  0.098  1.0
  O  O33  1  0.707  0.229  0.402  1.0
  O  O34  1  0.207  0.271  0.902  1.0
  O  O35  1  0.293  0.771  0.598  1.0
  O  O36  1  0.275  0.003  0.089  1.0
  O  O37  1  0.225  0.503  0.411  1.0
  O  O38  1  0.725  0.997  0.911  1.0
  O  O39  1  0.775  0.497  0.589  1.0
  O  O40  1  0.329  0.502  0.104  1.0
  O  O41  1  0.171  0.002  0.396  1.0
  O  O42  1  0.671  0.498  0.896  1.0
  O  O43  1  0.829  0.998  0.604  1.0
[/CIF]
.
The structure described by Na2U2O7 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms to form distorted NaO6 octahedra that share corners with four equivalent U(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-56°. In the third Na site, Na(3) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form UO6 octahedra that share corners with two equivalent Na(2)O6 octahedra and corners with two equivalent U(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-56°. In the second U site, U(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(6), one O(7), and two equivalent O(3) atoms. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Na(3), and one U(1) atom. In the second O site, O(6) is bonded to one Na(1), two equivalent Na(3), and one U(2) atom to form distorted ONa3U tetrahedra that share  a cornercorner with one O(6)Na3U tetrahedra,  a cornercorner with one O(1)NaU3 trigonal pyramid, corners with two equivalent O(3)NaU3 trigonal pyramids,  an edgeedge with one O(6)Na3U tetrahedra,  an edgeedge with one O(1)NaU3 trigonal pyramid, and  an edgeedge with one O(3)NaU3 trigonal pyramid. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(3), and one U(2) atom. In the fourth O site, O(1) is bonded to one Na(1), one U(2), and two equivalent U(1) atoms to form distorted ONaU3 trigonal pyramids that share  a cornercorner with one O(6)Na3U tetrahedra, corners with two equivalent O(3)NaU3 trigonal pyramids, corners with three equivalent O(1)NaU3 trigonal pyramids,  an edgeedge with one O(6)Na3U tetrahedra, and  an edgeedge with one O(3)NaU3 trigonal pyramid. In the fifth O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(3), one U(1), and one U(2) atom. In the sixth O site, O(3) is bonded to one Na(3), one U(1), and two equivalent U(2) atoms to form distorted ONaU3 trigonal pyramids that share corners with two equivalent O(6)Na3U tetrahedra, corners with two equivalent O(1)NaU3 trigonal pyramids, corners with two equivalent O(3)NaU3 trigonal pyramids,  an edgeedge with one O(6)Na3U tetrahedra, and  an edgeedge with one O(1)NaU3 trigonal pyramid. In the seventh O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Na(3), and one U(1) atom. is represented by the CIF file [CIF]
data_Na2U2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.928
_cell_length_b   7.920
_cell_length_c   12.453
_cell_angle_alpha   90.000
_cell_angle_beta   79.331
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   671.456
_cell_formula_units_Z   4
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  0.500  1.0
  Na  Na1  1  0.000  0.000  0.000  1.0
  Na  Na2  1  0.000  0.500  0.000  1.0
  Na  Na3  1  0.500  0.000  0.500  1.0
  Na  Na4  1  1.000  0.746  0.506  1.0
  Na  Na5  1  0.500  0.246  0.994  1.0
  Na  Na6  1  0.000  0.254  0.494  1.0
  Na  Na7  1  0.500  0.754  0.006  1.0
  U  U8  1  0.739  0.752  0.252  1.0
  U  U9  1  0.761  0.252  0.248  1.0
  U  U10  1  0.261  0.248  0.748  1.0
  U  U11  1  0.239  0.748  0.752  1.0
  U  U12  1  0.280  0.507  0.256  1.0
  U  U13  1  0.220  0.007  0.244  1.0
  U  U14  1  0.720  0.493  0.744  1.0
  U  U15  1  0.780  0.993  0.756  1.0
  O  O16  1  0.610  0.499  0.270  1.0
  O  O17  1  0.890  0.999  0.230  1.0
  O  O18  1  0.390  0.501  0.730  1.0
  O  O19  1  0.110  0.001  0.770  1.0
  O  O20  1  0.463  0.180  0.238  1.0
  O  O21  1  0.037  0.680  0.262  1.0
  O  O22  1  0.537  0.820  0.762  1.0
  O  O23  1  0.963  0.320  0.738  1.0
  O  O24  1  0.421  0.784  0.241  1.0
  O  O25  1  0.079  0.284  0.259  1.0
  O  O26  1  0.579  0.216  0.759  1.0
  O  O27  1  0.921  0.716  0.741  1.0
  O  O28  1  0.820  0.276  0.094  1.0
  O  O29  1  0.680  0.776  0.406  1.0
  O  O30  1  0.180  0.724  0.906  1.0
  O  O31  1  0.320  0.224  0.594  1.0
  O  O32  1  0.793  0.729  0.098  1.0
  O  O33  1  0.707  0.229  0.402  1.0
  O  O34  1  0.207  0.271  0.902  1.0
  O  O35  1  0.293  0.771  0.598  1.0
  O  O36  1  0.275  0.003  0.089  1.0
  O  O37  1  0.225  0.503  0.411  1.0
  O  O38  1  0.725  0.997  0.911  1.0
  O  O39  1  0.775  0.497  0.589  1.0
  O  O40  1  0.329  0.502  0.104  1.0
  O  O41  1  0.171  0.002  0.396  1.0
  O  O42  1  0.671  0.498  0.896  1.0
  O  O43  1  0.829  0.998  0.604  1.0
[/CIF]
.