The compound described by H2P2O7Na2 crystallizes in the orthorhombic Fddd space group. Na(1) is bonded to one O(1), two equivalent O(2), and three equivalent O(3) atoms to form distorted NaO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with four equivalent Na(1)O6 octahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with six equivalent Na(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-63°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to two equivalent O(1) atoms. In the second H site, H(2) is bonded in a linear geometry to two equivalent O(2) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(1), one P(1), and one H(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Na(1), one P(1), and one H(2) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Na(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. is represented by the CIF card [CIF]
data_Na2P2H2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   15.219
_cell_length_b   14.320
_cell_length_c   7.115
_cell_angle_alpha   83.223
_cell_angle_beta   69.119
_cell_angle_gamma   27.659
_symmetry_Int_Tables_number   1
_cell_volume   598.551
_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  0.910  0.991  0.308  1.0
  Na  Na1  1  0.991  0.910  0.791  1.0
  Na  Na2  1  0.308  0.791  0.910  1.0
  Na  Na3  1  0.791  0.308  0.991  1.0
  Na  Na4  1  0.340  0.259  0.942  1.0
  Na  Na5  1  0.259  0.340  0.459  1.0
  Na  Na6  1  0.942  0.459  0.340  1.0
  Na  Na7  1  0.459  0.942  0.259  1.0
  P  P8  1  0.412  0.446  0.873  1.0
  P  P9  1  0.446  0.412  0.270  1.0
  P  P10  1  0.873  0.270  0.412  1.0
  P  P11  1  0.270  0.873  0.446  1.0
  P  P12  1  0.838  0.804  0.377  1.0
  P  P13  1  0.804  0.838  0.980  1.0
  P  P14  1  0.377  0.980  0.838  1.0
  P  P15  1  0.980  0.377  0.804  1.0
  H  H16  1  0.385  0.385  0.615  1.0
  H  H17  1  0.615  0.615  0.385  1.0
  H  H18  1  0.865  0.865  0.635  1.0
  H  H19  1  0.635  0.635  0.865  1.0
  H  H20  1  0.676  0.324  0.676  1.0
  H  H21  1  0.324  0.676  0.324  1.0
  H  H22  1  0.574  0.926  0.574  1.0
  H  H23  1  0.926  0.574  0.926  1.0
  O  O24  1  0.363  0.403  0.796  1.0
  O  O25  1  0.403  0.363  0.437  1.0
  O  O26  1  0.796  0.437  0.363  1.0
  O  O27  1  0.437  0.796  0.403  1.0
  O  O28  1  0.887  0.847  0.454  1.0
  O  O29  1  0.847  0.887  0.813  1.0
  O  O30  1  0.454  0.813  0.887  1.0
  O  O31  1  0.813  0.454  0.847  1.0
  O  O32  1  0.658  0.256  0.697  1.0
  O  O33  1  0.256  0.658  0.388  1.0
  O  O34  1  0.697  0.388  0.658  1.0
  O  O35  1  0.388  0.697  0.256  1.0
  O  O36  1  0.592  0.994  0.553  1.0
  O  O37  1  0.994  0.592  0.862  1.0
  O  O38  1  0.553  0.862  0.592  1.0
  O  O39  1  0.862  0.553  0.994  1.0
  O  O40  1  0.241  0.680  0.936  1.0
  O  O41  1  0.680  0.241  0.144  1.0
  O  O42  1  0.936  0.144  0.241  1.0
  O  O43  1  0.144  0.936  0.680  1.0
  O  O44  1  0.009  0.570  0.314  1.0
  O  O45  1  0.570  0.009  0.106  1.0
  O  O46  1  0.314  0.106  0.009  1.0
  O  O47  1  0.106  0.314  0.570  1.0
  O  O48  1  0.404  0.404  0.096  1.0
  O  O49  1  0.096  0.096  0.404  1.0
  O  O50  1  0.846  0.846  0.154  1.0
  O  O51  1  0.154  0.154  0.846  1.0
[/CIF]
.
The compound described by H2P2O7Na2 crystallizes in the orthorhombic Fddd space group. Na(1) is bonded to one O(1), two equivalent O(2), and three equivalent O(3) atoms to form distorted NaO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with four equivalent Na(1)O6 octahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with six equivalent Na(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-63°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to two equivalent O(1) atoms. In the second H site, H(2) is bonded in a linear geometry to two equivalent O(2) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(1), one P(1), and one H(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Na(1), one P(1), and one H(2) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Na(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. is represented by the CIF card [CIF]
data_Na2P2H2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   15.219
_cell_length_b   14.320
_cell_length_c   7.115
_cell_angle_alpha   83.223
_cell_angle_beta   69.119
_cell_angle_gamma   27.659
_symmetry_Int_Tables_number   1
_cell_volume   598.551
_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  0.910  0.991  0.308  1.0
  Na  Na1  1  0.991  0.910  0.791  1.0
  Na  Na2  1  0.308  0.791  0.910  1.0
  Na  Na3  1  0.791  0.308  0.991  1.0
  Na  Na4  1  0.340  0.259  0.942  1.0
  Na  Na5  1  0.259  0.340  0.459  1.0
  Na  Na6  1  0.942  0.459  0.340  1.0
  Na  Na7  1  0.459  0.942  0.259  1.0
  P  P8  1  0.412  0.446  0.873  1.0
  P  P9  1  0.446  0.412  0.270  1.0
  P  P10  1  0.873  0.270  0.412  1.0
  P  P11  1  0.270  0.873  0.446  1.0
  P  P12  1  0.838  0.804  0.377  1.0
  P  P13  1  0.804  0.838  0.980  1.0
  P  P14  1  0.377  0.980  0.838  1.0
  P  P15  1  0.980  0.377  0.804  1.0
  H  H16  1  0.385  0.385  0.615  1.0
  H  H17  1  0.615  0.615  0.385  1.0
  H  H18  1  0.865  0.865  0.635  1.0
  H  H19  1  0.635  0.635  0.865  1.0
  H  H20  1  0.676  0.324  0.676  1.0
  H  H21  1  0.324  0.676  0.324  1.0
  H  H22  1  0.574  0.926  0.574  1.0
  H  H23  1  0.926  0.574  0.926  1.0
  O  O24  1  0.363  0.403  0.796  1.0
  O  O25  1  0.403  0.363  0.437  1.0
  O  O26  1  0.796  0.437  0.363  1.0
  O  O27  1  0.437  0.796  0.403  1.0
  O  O28  1  0.887  0.847  0.454  1.0
  O  O29  1  0.847  0.887  0.813  1.0
  O  O30  1  0.454  0.813  0.887  1.0
  O  O31  1  0.813  0.454  0.847  1.0
  O  O32  1  0.658  0.256  0.697  1.0
  O  O33  1  0.256  0.658  0.388  1.0
  O  O34  1  0.697  0.388  0.658  1.0
  O  O35  1  0.388  0.697  0.256  1.0
  O  O36  1  0.592  0.994  0.553  1.0
  O  O37  1  0.994  0.592  0.862  1.0
  O  O38  1  0.553  0.862  0.592  1.0
  O  O39  1  0.862  0.553  0.994  1.0
  O  O40  1  0.241  0.680  0.936  1.0
  O  O41  1  0.680  0.241  0.144  1.0
  O  O42  1  0.936  0.144  0.241  1.0
  O  O43  1  0.144  0.936  0.680  1.0
  O  O44  1  0.009  0.570  0.314  1.0
  O  O45  1  0.570  0.009  0.106  1.0
  O  O46  1  0.314  0.106  0.009  1.0
  O  O47  1  0.106  0.314  0.570  1.0
  O  O48  1  0.404  0.404  0.096  1.0
  O  O49  1  0.096  0.096  0.404  1.0
  O  O50  1  0.846  0.846  0.154  1.0
  O  O51  1  0.154  0.154  0.846  1.0
[/CIF]
.