The compound described by Li2NiP2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to one O(2), one O(4), and two equivalent O(1) atoms. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(4), one O(6), one O(7), and two equivalent O(5) atoms. Ni(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-62°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-55°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Ni(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Li(2), one Ni(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(2), one Ni(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Li(2), one Ni(1), and one P(2) atom. is represented by the CIF card [CIF]
data_Li2NiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.038
_cell_length_b   8.127
_cell_length_c   13.777
_cell_angle_alpha   68.887
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   526.291
_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
  Li  Li0  1  0.206  0.983  0.671  1.0
  Li  Li1  1  0.294  0.983  0.171  1.0
  Li  Li2  1  0.734  0.426  0.840  1.0
  Li  Li3  1  0.234  0.574  0.660  1.0
  Li  Li4  1  0.766  0.426  0.340  1.0
  Li  Li5  1  0.266  0.574  0.160  1.0
  Li  Li6  1  0.706  0.017  0.829  1.0
  Li  Li7  1  0.794  0.017  0.329  1.0
  Ni  Ni8  1  0.269  0.720  0.867  1.0
  Ni  Ni9  1  0.231  0.720  0.367  1.0
  Ni  Ni10  1  0.769  0.280  0.633  1.0
  Ni  Ni11  1  0.731  0.280  0.133  1.0
  P  P12  1  0.722  0.817  0.695  1.0
  P  P13  1  0.726  0.697  0.521  1.0
  P  P14  1  0.778  0.817  0.195  1.0
  P  P15  1  0.226  0.303  0.979  1.0
  P  P16  1  0.774  0.697  0.021  1.0
  P  P17  1  0.222  0.183  0.805  1.0
  P  P18  1  0.274  0.303  0.479  1.0
  P  P19  1  0.278  0.183  0.305  1.0
  O  O20  1  0.252  0.997  0.805  1.0
  O  O21  1  0.248  0.997  0.305  1.0
  O  O22  1  0.631  0.779  0.917  1.0
  O  O23  1  0.771  0.847  0.573  1.0
  O  O24  1  0.435  0.749  0.718  1.0
  O  O25  1  0.931  0.689  0.761  1.0
  O  O26  1  0.427  0.678  0.509  1.0
  O  O27  1  0.869  0.779  0.417  1.0
  O  O28  1  0.729  0.847  0.073  1.0
  O  O29  1  0.362  0.466  0.903  1.0
  O  O30  1  0.065  0.749  0.218  1.0
  O  O31  1  0.569  0.689  0.261  1.0
  O  O32  1  0.862  0.534  0.597  1.0
  O  O33  1  0.073  0.678  0.009  1.0
  O  O34  1  0.927  0.322  0.991  1.0
  O  O35  1  0.138  0.466  0.403  1.0
  O  O36  1  0.431  0.311  0.739  1.0
  O  O37  1  0.935  0.251  0.782  1.0
  O  O38  1  0.638  0.534  0.097  1.0
  O  O39  1  0.271  0.153  0.927  1.0
  O  O40  1  0.131  0.221  0.583  1.0
  O  O41  1  0.573  0.322  0.491  1.0
  O  O42  1  0.069  0.311  0.239  1.0
  O  O43  1  0.565  0.251  0.282  1.0
  O  O44  1  0.229  0.153  0.427  1.0
  O  O45  1  0.369  0.221  0.083  1.0
  O  O46  1  0.752  0.003  0.695  1.0
  O  O47  1  0.748  0.003  0.195  1.0
[/CIF]
.
The compound described by Li2NiP2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to one O(2), one O(4), and two equivalent O(1) atoms. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(4), one O(6), one O(7), and two equivalent O(5) atoms. Ni(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-62°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-55°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Ni(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Li(2), one Ni(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(2), one Ni(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Li(2), one Ni(1), and one P(2) atom. is represented by the CIF card [CIF]
data_Li2NiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.038
_cell_length_b   8.127
_cell_length_c   13.777
_cell_angle_alpha   68.887
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   526.291
_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
  Li  Li0  1  0.206  0.983  0.671  1.0
  Li  Li1  1  0.294  0.983  0.171  1.0
  Li  Li2  1  0.734  0.426  0.840  1.0
  Li  Li3  1  0.234  0.574  0.660  1.0
  Li  Li4  1  0.766  0.426  0.340  1.0
  Li  Li5  1  0.266  0.574  0.160  1.0
  Li  Li6  1  0.706  0.017  0.829  1.0
  Li  Li7  1  0.794  0.017  0.329  1.0
  Ni  Ni8  1  0.269  0.720  0.867  1.0
  Ni  Ni9  1  0.231  0.720  0.367  1.0
  Ni  Ni10  1  0.769  0.280  0.633  1.0
  Ni  Ni11  1  0.731  0.280  0.133  1.0
  P  P12  1  0.722  0.817  0.695  1.0
  P  P13  1  0.726  0.697  0.521  1.0
  P  P14  1  0.778  0.817  0.195  1.0
  P  P15  1  0.226  0.303  0.979  1.0
  P  P16  1  0.774  0.697  0.021  1.0
  P  P17  1  0.222  0.183  0.805  1.0
  P  P18  1  0.274  0.303  0.479  1.0
  P  P19  1  0.278  0.183  0.305  1.0
  O  O20  1  0.252  0.997  0.805  1.0
  O  O21  1  0.248  0.997  0.305  1.0
  O  O22  1  0.631  0.779  0.917  1.0
  O  O23  1  0.771  0.847  0.573  1.0
  O  O24  1  0.435  0.749  0.718  1.0
  O  O25  1  0.931  0.689  0.761  1.0
  O  O26  1  0.427  0.678  0.509  1.0
  O  O27  1  0.869  0.779  0.417  1.0
  O  O28  1  0.729  0.847  0.073  1.0
  O  O29  1  0.362  0.466  0.903  1.0
  O  O30  1  0.065  0.749  0.218  1.0
  O  O31  1  0.569  0.689  0.261  1.0
  O  O32  1  0.862  0.534  0.597  1.0
  O  O33  1  0.073  0.678  0.009  1.0
  O  O34  1  0.927  0.322  0.991  1.0
  O  O35  1  0.138  0.466  0.403  1.0
  O  O36  1  0.431  0.311  0.739  1.0
  O  O37  1  0.935  0.251  0.782  1.0
  O  O38  1  0.638  0.534  0.097  1.0
  O  O39  1  0.271  0.153  0.927  1.0
  O  O40  1  0.131  0.221  0.583  1.0
  O  O41  1  0.573  0.322  0.491  1.0
  O  O42  1  0.069  0.311  0.239  1.0
  O  O43  1  0.565  0.251  0.282  1.0
  O  O44  1  0.229  0.153  0.427  1.0
  O  O45  1  0.369  0.221  0.083  1.0
  O  O46  1  0.752  0.003  0.695  1.0
  O  O47  1  0.748  0.003  0.195  1.0
[/CIF]
.