The structure described by Li2NiP2O7 crystallizes in the monoclinic C2/c space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form LiO4 tetrahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  a cornercorner with one Li(3)O4 trigonal pyramid. In the second Li site, Li(2) is bonded to two equivalent O(3) and two equivalent O(7) atoms to form distorted LiO4 trigonal pyramids that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. In the third Li site, Li(3) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form distorted LiO4 trigonal pyramids that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. Ni(1) is bonded in a rectangular see-saw-like geometry to one O(2), one O(3), one O(4), and one O(5) atom. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  a cornercorner with one Li(3)O4 trigonal pyramid. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  a cornercorner with one Li(3)O4 trigonal pyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Li(1), one Ni(1), and one P(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(2), one Ni(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Li(3), one Ni(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Li(1), one Li(3), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(1), one Li(2), and one P(1) atom. is represented by the CIF card [CIF]
data_Li2NiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.560
_cell_length_b   7.560
_cell_length_c   10.960
_cell_angle_alpha   88.746
_cell_angle_beta   88.746
_cell_angle_gamma   117.150
_symmetry_Int_Tables_number   1
_cell_volume   556.880
_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  0.719  0.295  0.998  1.0
  Li  Li1  1  0.295  0.719  0.498  1.0
  Li  Li2  1  0.716  0.284  0.750  1.0
  Li  Li3  1  0.293  0.707  0.750  1.0
  Li  Li4  1  0.707  0.293  0.250  1.0
  Li  Li5  1  0.284  0.716  0.250  1.0
  Li  Li6  1  0.705  0.281  0.502  1.0
  Li  Li7  1  0.281  0.705  0.002  1.0
  Ni  Ni8  1  0.697  0.696  0.887  1.0
  Ni  Ni9  1  0.696  0.697  0.387  1.0
  Ni  Ni10  1  0.304  0.303  0.613  1.0
  Ni  Ni11  1  0.303  0.304  0.113  1.0
  P  P12  1  0.703  0.915  0.632  1.0
  P  P13  1  0.915  0.703  0.132  1.0
  P  P14  1  0.909  0.682  0.634  1.0
  P  P15  1  0.682  0.909  0.134  1.0
  P  P16  1  0.318  0.091  0.866  1.0
  P  P17  1  0.091  0.318  0.366  1.0
  P  P18  1  0.085  0.297  0.868  1.0
  P  P19  1  0.297  0.085  0.368  1.0
  O  O20  1  0.914  0.901  0.627  1.0
  O  O21  1  0.901  0.914  0.127  1.0
  O  O22  1  0.585  0.803  0.521  1.0
  O  O23  1  0.803  0.585  0.021  1.0
  O  O24  1  0.802  0.580  0.757  1.0
  O  O25  1  0.580  0.802  0.257  1.0
  O  O26  1  0.592  0.803  0.752  1.0
  O  O27  1  0.803  0.592  0.252  1.0
  O  O28  1  0.782  0.569  0.525  1.0
  O  O29  1  0.569  0.782  0.025  1.0
  O  O30  1  0.281  0.878  0.874  1.0
  O  O31  1  0.878  0.281  0.374  1.0
  O  O32  1  0.867  0.242  0.874  1.0
  O  O33  1  0.242  0.867  0.374  1.0
  O  O34  1  0.758  0.133  0.626  1.0
  O  O35  1  0.133  0.758  0.126  1.0
  O  O36  1  0.122  0.719  0.626  1.0
  O  O37  1  0.719  0.122  0.126  1.0
  O  O38  1  0.431  0.218  0.975  1.0
  O  O39  1  0.218  0.431  0.475  1.0
  O  O40  1  0.197  0.408  0.748  1.0
  O  O41  1  0.408  0.197  0.248  1.0
  O  O42  1  0.420  0.198  0.743  1.0
  O  O43  1  0.198  0.420  0.243  1.0
  O  O44  1  0.197  0.415  0.979  1.0
  O  O45  1  0.415  0.197  0.479  1.0
  O  O46  1  0.099  0.086  0.873  1.0
  O  O47  1  0.086  0.099  0.373  1.0
[/CIF]
.
The structure described by Li2NiP2O7 crystallizes in the monoclinic C2/c space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form LiO4 tetrahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  a cornercorner with one Li(3)O4 trigonal pyramid. In the second Li site, Li(2) is bonded to two equivalent O(3) and two equivalent O(7) atoms to form distorted LiO4 trigonal pyramids that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. In the third Li site, Li(3) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form distorted LiO4 trigonal pyramids that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. Ni(1) is bonded in a rectangular see-saw-like geometry to one O(2), one O(3), one O(4), and one O(5) atom. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  a cornercorner with one Li(3)O4 trigonal pyramid. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  a cornercorner with one Li(3)O4 trigonal pyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Li(1), one Ni(1), and one P(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(2), one Ni(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Li(3), one Ni(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Li(1), one Li(3), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(1), one Li(2), and one P(1) atom. is represented by the CIF card [CIF]
data_Li2NiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.560
_cell_length_b   7.560
_cell_length_c   10.960
_cell_angle_alpha   88.746
_cell_angle_beta   88.746
_cell_angle_gamma   117.150
_symmetry_Int_Tables_number   1
_cell_volume   556.880
_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  0.719  0.295  0.998  1.0
  Li  Li1  1  0.295  0.719  0.498  1.0
  Li  Li2  1  0.716  0.284  0.750  1.0
  Li  Li3  1  0.293  0.707  0.750  1.0
  Li  Li4  1  0.707  0.293  0.250  1.0
  Li  Li5  1  0.284  0.716  0.250  1.0
  Li  Li6  1  0.705  0.281  0.502  1.0
  Li  Li7  1  0.281  0.705  0.002  1.0
  Ni  Ni8  1  0.697  0.696  0.887  1.0
  Ni  Ni9  1  0.696  0.697  0.387  1.0
  Ni  Ni10  1  0.304  0.303  0.613  1.0
  Ni  Ni11  1  0.303  0.304  0.113  1.0
  P  P12  1  0.703  0.915  0.632  1.0
  P  P13  1  0.915  0.703  0.132  1.0
  P  P14  1  0.909  0.682  0.634  1.0
  P  P15  1  0.682  0.909  0.134  1.0
  P  P16  1  0.318  0.091  0.866  1.0
  P  P17  1  0.091  0.318  0.366  1.0
  P  P18  1  0.085  0.297  0.868  1.0
  P  P19  1  0.297  0.085  0.368  1.0
  O  O20  1  0.914  0.901  0.627  1.0
  O  O21  1  0.901  0.914  0.127  1.0
  O  O22  1  0.585  0.803  0.521  1.0
  O  O23  1  0.803  0.585  0.021  1.0
  O  O24  1  0.802  0.580  0.757  1.0
  O  O25  1  0.580  0.802  0.257  1.0
  O  O26  1  0.592  0.803  0.752  1.0
  O  O27  1  0.803  0.592  0.252  1.0
  O  O28  1  0.782  0.569  0.525  1.0
  O  O29  1  0.569  0.782  0.025  1.0
  O  O30  1  0.281  0.878  0.874  1.0
  O  O31  1  0.878  0.281  0.374  1.0
  O  O32  1  0.867  0.242  0.874  1.0
  O  O33  1  0.242  0.867  0.374  1.0
  O  O34  1  0.758  0.133  0.626  1.0
  O  O35  1  0.133  0.758  0.126  1.0
  O  O36  1  0.122  0.719  0.626  1.0
  O  O37  1  0.719  0.122  0.126  1.0
  O  O38  1  0.431  0.218  0.975  1.0
  O  O39  1  0.218  0.431  0.475  1.0
  O  O40  1  0.197  0.408  0.748  1.0
  O  O41  1  0.408  0.197  0.248  1.0
  O  O42  1  0.420  0.198  0.743  1.0
  O  O43  1  0.198  0.420  0.243  1.0
  O  O44  1  0.197  0.415  0.979  1.0
  O  O45  1  0.415  0.197  0.479  1.0
  O  O46  1  0.099  0.086  0.873  1.0
  O  O47  1  0.086  0.099  0.373  1.0
[/CIF]
.