The compound described by Na2Ni3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(6), and one O(7) atom. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. In the second Ni site, Ni(2) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(6), one O(7), and two equivalent O(2) atoms. There are two inequivalent P sites. In the first P site, 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 two equivalent Ni(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-61°. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Ni(1), one Ni(2), and one P(1) atom to form distorted corner-sharing ONaNi2P trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Ni(2) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Ni(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Ni(1), one Ni(2), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom. is represented by the CIF file [CIF]
data_Na2Ni3(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.228
_cell_length_b   7.409
_cell_length_c   9.501
_cell_angle_alpha   68.559
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   539.138
_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  0.418  0.690  0.878  1.0
  Na  Na1  1  0.082  0.690  0.378  1.0
  Na  Na2  1  0.918  0.310  0.622  1.0
  Na  Na3  1  0.582  0.310  0.122  1.0
  Ni  Ni4  1  0.000  0.000  0.500  1.0
  Ni  Ni5  1  0.382  0.821  0.514  1.0
  Ni  Ni6  1  0.500  0.000  0.000  1.0
  Ni  Ni7  1  0.118  0.821  0.014  1.0
  Ni  Ni8  1  0.882  0.179  0.986  1.0
  Ni  Ni9  1  0.618  0.179  0.486  1.0
  P  P10  1  0.799  0.890  0.806  1.0
  P  P11  1  0.701  0.890  0.306  1.0
  P  P12  1  0.040  0.601  0.791  1.0
  P  P13  1  0.540  0.399  0.709  1.0
  P  P14  1  0.460  0.601  0.291  1.0
  P  P15  1  0.960  0.399  0.209  1.0
  P  P16  1  0.299  0.110  0.694  1.0
  P  P17  1  0.201  0.110  0.194  1.0
  O  O18  1  0.297  0.988  0.866  1.0
  O  O19  1  0.924  0.975  0.886  1.0
  O  O20  1  0.636  0.861  0.884  1.0
  O  O21  1  0.203  0.988  0.366  1.0
  O  O22  1  0.576  0.975  0.386  1.0
  O  O23  1  0.862  0.683  0.813  1.0
  O  O24  1  0.151  0.630  0.909  1.0
  O  O25  1  0.864  0.861  0.384  1.0
  O  O26  1  0.099  0.721  0.628  1.0
  O  O27  1  0.507  0.611  0.686  1.0
  O  O28  1  0.638  0.683  0.313  1.0
  O  O29  1  0.349  0.630  0.409  1.0
  O  O30  1  0.401  0.721  0.128  1.0
  O  O31  1  0.007  0.389  0.814  1.0
  O  O32  1  0.993  0.611  0.186  1.0
  O  O33  1  0.599  0.279  0.872  1.0
  O  O34  1  0.651  0.370  0.591  1.0
  O  O35  1  0.362  0.317  0.687  1.0
  O  O36  1  0.493  0.389  0.314  1.0
  O  O37  1  0.901  0.279  0.372  1.0
  O  O38  1  0.136  0.139  0.616  1.0
  O  O39  1  0.849  0.370  0.091  1.0
  O  O40  1  0.138  0.317  0.187  1.0
  O  O41  1  0.424  0.025  0.614  1.0
  O  O42  1  0.797  0.012  0.634  1.0
  O  O43  1  0.364  0.139  0.116  1.0
  O  O44  1  0.076  0.025  0.114  1.0
  O  O45  1  0.703  0.012  0.134  1.0
[/CIF]
.
The compound described by Na2Ni3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(6), and one O(7) atom. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. In the second Ni site, Ni(2) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(6), one O(7), and two equivalent O(2) atoms. There are two inequivalent P sites. In the first P site, 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 two equivalent Ni(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-61°. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Ni(1), one Ni(2), and one P(1) atom to form distorted corner-sharing ONaNi2P trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Ni(2) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Ni(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Ni(1), one Ni(2), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom. is represented by the CIF file [CIF]
data_Na2Ni3(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.228
_cell_length_b   7.409
_cell_length_c   9.501
_cell_angle_alpha   68.559
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   539.138
_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  0.418  0.690  0.878  1.0
  Na  Na1  1  0.082  0.690  0.378  1.0
  Na  Na2  1  0.918  0.310  0.622  1.0
  Na  Na3  1  0.582  0.310  0.122  1.0
  Ni  Ni4  1  0.000  0.000  0.500  1.0
  Ni  Ni5  1  0.382  0.821  0.514  1.0
  Ni  Ni6  1  0.500  0.000  0.000  1.0
  Ni  Ni7  1  0.118  0.821  0.014  1.0
  Ni  Ni8  1  0.882  0.179  0.986  1.0
  Ni  Ni9  1  0.618  0.179  0.486  1.0
  P  P10  1  0.799  0.890  0.806  1.0
  P  P11  1  0.701  0.890  0.306  1.0
  P  P12  1  0.040  0.601  0.791  1.0
  P  P13  1  0.540  0.399  0.709  1.0
  P  P14  1  0.460  0.601  0.291  1.0
  P  P15  1  0.960  0.399  0.209  1.0
  P  P16  1  0.299  0.110  0.694  1.0
  P  P17  1  0.201  0.110  0.194  1.0
  O  O18  1  0.297  0.988  0.866  1.0
  O  O19  1  0.924  0.975  0.886  1.0
  O  O20  1  0.636  0.861  0.884  1.0
  O  O21  1  0.203  0.988  0.366  1.0
  O  O22  1  0.576  0.975  0.386  1.0
  O  O23  1  0.862  0.683  0.813  1.0
  O  O24  1  0.151  0.630  0.909  1.0
  O  O25  1  0.864  0.861  0.384  1.0
  O  O26  1  0.099  0.721  0.628  1.0
  O  O27  1  0.507  0.611  0.686  1.0
  O  O28  1  0.638  0.683  0.313  1.0
  O  O29  1  0.349  0.630  0.409  1.0
  O  O30  1  0.401  0.721  0.128  1.0
  O  O31  1  0.007  0.389  0.814  1.0
  O  O32  1  0.993  0.611  0.186  1.0
  O  O33  1  0.599  0.279  0.872  1.0
  O  O34  1  0.651  0.370  0.591  1.0
  O  O35  1  0.362  0.317  0.687  1.0
  O  O36  1  0.493  0.389  0.314  1.0
  O  O37  1  0.901  0.279  0.372  1.0
  O  O38  1  0.136  0.139  0.616  1.0
  O  O39  1  0.849  0.370  0.091  1.0
  O  O40  1  0.138  0.317  0.187  1.0
  O  O41  1  0.424  0.025  0.614  1.0
  O  O42  1  0.797  0.012  0.634  1.0
  O  O43  1  0.364  0.139  0.116  1.0
  O  O44  1  0.076  0.025  0.114  1.0
  O  O45  1  0.703  0.012  0.134  1.0
[/CIF]
.