The structure described by MgNi3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and  an edgeedge with one Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, 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 51-65°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Ni(2)O6 octahedra, 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 39-61°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Mg(1), one Ni(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Mg(1), one Ni(1), one Ni(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgNi3(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.498
_cell_length_b   7.265
_cell_length_c   9.486
_cell_angle_alpha   67.640
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   477.880
_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
  Mg  Mg0  1  0.000  0.500  0.000  1.0
  Mg  Mg1  1  0.500  0.500  0.500  1.0
  Ni  Ni2  1  0.128  0.814  0.523  1.0
  Ni  Ni3  1  0.628  0.186  0.977  1.0
  Ni  Ni4  1  0.872  0.186  0.477  1.0
  Ni  Ni5  1  0.372  0.814  0.023  1.0
  Ni  Ni6  1  0.000  0.000  0.000  1.0
  Ni  Ni7  1  0.500  0.000  0.500  1.0
  P  P8  1  0.923  0.411  0.704  1.0
  P  P9  1  0.423  0.589  0.796  1.0
  P  P10  1  0.077  0.589  0.296  1.0
  P  P11  1  0.577  0.411  0.204  1.0
  P  P12  1  0.207  0.131  0.687  1.0
  P  P13  1  0.707  0.869  0.813  1.0
  P  P14  1  0.793  0.869  0.313  1.0
  P  P15  1  0.293  0.131  0.187  1.0
  O  O16  1  0.383  0.194  0.599  1.0
  O  O17  1  0.883  0.806  0.901  1.0
  O  O18  1  0.617  0.806  0.401  1.0
  O  O19  1  0.117  0.194  0.099  1.0
  O  O20  1  0.379  0.720  0.626  1.0
  O  O21  1  0.879  0.280  0.874  1.0
  O  O22  1  0.621  0.280  0.374  1.0
  O  O23  1  0.121  0.720  0.126  1.0
  O  O24  1  0.787  0.385  0.593  1.0
  O  O25  1  0.287  0.615  0.907  1.0
  O  O26  1  0.213  0.615  0.407  1.0
  O  O27  1  0.713  0.385  0.093  1.0
  O  O28  1  0.113  0.335  0.670  1.0
  O  O29  1  0.613  0.665  0.830  1.0
  O  O30  1  0.887  0.665  0.330  1.0
  O  O31  1  0.387  0.335  0.170  1.0
  O  O32  1  0.531  0.620  0.193  1.0
  O  O33  1  0.031  0.380  0.307  1.0
  O  O34  1  0.469  0.380  0.807  1.0
  O  O35  1  0.969  0.620  0.693  1.0
  O  O36  1  0.785  0.984  0.140  1.0
  O  O37  1  0.285  0.016  0.360  1.0
  O  O38  1  0.215  0.016  0.860  1.0
  O  O39  1  0.715  0.984  0.640  1.0
  O  O40  1  0.418  0.032  0.109  1.0
  O  O41  1  0.918  0.968  0.391  1.0
  O  O42  1  0.582  0.968  0.891  1.0
  O  O43  1  0.082  0.032  0.609  1.0
[/CIF]
.
The structure described by MgNi3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and  an edgeedge with one Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, 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 51-65°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Ni(2)O6 octahedra, 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 39-61°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Mg(1), one Ni(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Mg(1), one Ni(1), one Ni(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgNi3(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.498
_cell_length_b   7.265
_cell_length_c   9.486
_cell_angle_alpha   67.640
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   477.880
_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
  Mg  Mg0  1  0.000  0.500  0.000  1.0
  Mg  Mg1  1  0.500  0.500  0.500  1.0
  Ni  Ni2  1  0.128  0.814  0.523  1.0
  Ni  Ni3  1  0.628  0.186  0.977  1.0
  Ni  Ni4  1  0.872  0.186  0.477  1.0
  Ni  Ni5  1  0.372  0.814  0.023  1.0
  Ni  Ni6  1  0.000  0.000  0.000  1.0
  Ni  Ni7  1  0.500  0.000  0.500  1.0
  P  P8  1  0.923  0.411  0.704  1.0
  P  P9  1  0.423  0.589  0.796  1.0
  P  P10  1  0.077  0.589  0.296  1.0
  P  P11  1  0.577  0.411  0.204  1.0
  P  P12  1  0.207  0.131  0.687  1.0
  P  P13  1  0.707  0.869  0.813  1.0
  P  P14  1  0.793  0.869  0.313  1.0
  P  P15  1  0.293  0.131  0.187  1.0
  O  O16  1  0.383  0.194  0.599  1.0
  O  O17  1  0.883  0.806  0.901  1.0
  O  O18  1  0.617  0.806  0.401  1.0
  O  O19  1  0.117  0.194  0.099  1.0
  O  O20  1  0.379  0.720  0.626  1.0
  O  O21  1  0.879  0.280  0.874  1.0
  O  O22  1  0.621  0.280  0.374  1.0
  O  O23  1  0.121  0.720  0.126  1.0
  O  O24  1  0.787  0.385  0.593  1.0
  O  O25  1  0.287  0.615  0.907  1.0
  O  O26  1  0.213  0.615  0.407  1.0
  O  O27  1  0.713  0.385  0.093  1.0
  O  O28  1  0.113  0.335  0.670  1.0
  O  O29  1  0.613  0.665  0.830  1.0
  O  O30  1  0.887  0.665  0.330  1.0
  O  O31  1  0.387  0.335  0.170  1.0
  O  O32  1  0.531  0.620  0.193  1.0
  O  O33  1  0.031  0.380  0.307  1.0
  O  O34  1  0.469  0.380  0.807  1.0
  O  O35  1  0.969  0.620  0.693  1.0
  O  O36  1  0.785  0.984  0.140  1.0
  O  O37  1  0.285  0.016  0.360  1.0
  O  O38  1  0.215  0.016  0.860  1.0
  O  O39  1  0.715  0.984  0.640  1.0
  O  O40  1  0.418  0.032  0.109  1.0
  O  O41  1  0.918  0.968  0.391  1.0
  O  O42  1  0.582  0.968  0.891  1.0
  O  O43  1  0.082  0.032  0.609  1.0
[/CIF]
.