The material structure described by Nb2Ni2O9 crystallizes in the hexagonal P6_3/mcm space group. Nb(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with six equivalent Ni(1)O6 octahedra and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. Ni(1) is bonded to six equivalent O(1) atoms to form NiO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and edges with three equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1) and two equivalent Ni(1) atoms. In the second O site, O(2) is bonded in an L-shaped geometry to two equivalent Nb(1) atoms. is represented by the CIF file [CIF]
data_Nb2Ni2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.847
_cell_length_b   4.847
_cell_length_c   14.218
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   289.228
_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
  Nb  Nb0  1  0.000  0.000  0.659  1.0
  Nb  Nb1  1  0.000  0.000  0.159  1.0
  Nb  Nb2  1  0.000  0.000  0.841  1.0
  Nb  Nb3  1  0.000  0.000  0.341  1.0
  Ni  Ni4  1  0.333  0.667  0.000  1.0
  Ni  Ni5  1  0.333  0.667  0.500  1.0
  Ni  Ni6  1  0.667  0.333  0.000  1.0
  Ni  Ni7  1  0.667  0.333  0.500  1.0
  O  O8  1  0.645  0.645  0.575  1.0
  O  O9  1  0.000  0.700  0.750  1.0
  O  O10  1  0.645  0.000  0.425  1.0
  O  O11  1  0.355  0.355  0.425  1.0
  O  O12  1  0.000  0.355  0.575  1.0
  O  O13  1  0.700  0.700  0.250  1.0
  O  O14  1  0.000  0.355  0.925  1.0
  O  O15  1  0.355  0.000  0.575  1.0
  O  O16  1  0.355  0.355  0.075  1.0
  O  O17  1  0.000  0.645  0.425  1.0
  O  O18  1  0.645  0.645  0.925  1.0
  O  O19  1  0.645  0.000  0.075  1.0
  O  O20  1  0.700  0.000  0.750  1.0
  O  O21  1  0.300  0.300  0.750  1.0
  O  O22  1  0.300  0.000  0.250  1.0
  O  O23  1  0.000  0.645  0.075  1.0
  O  O24  1  0.000  0.300  0.250  1.0
  O  O25  1  0.355  0.000  0.925  1.0
[/CIF]
.
The material structure described by Nb2Ni2O9 crystallizes in the hexagonal P6_3/mcm space group. Nb(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with six equivalent Ni(1)O6 octahedra and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. Ni(1) is bonded to six equivalent O(1) atoms to form NiO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and edges with three equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 51°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Nb(1) and two equivalent Ni(1) atoms. In the second O site, O(2) is bonded in an L-shaped geometry to two equivalent Nb(1) atoms. is represented by the CIF file [CIF]
data_Nb2Ni2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.847
_cell_length_b   4.847
_cell_length_c   14.218
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   289.228
_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
  Nb  Nb0  1  0.000  0.000  0.659  1.0
  Nb  Nb1  1  0.000  0.000  0.159  1.0
  Nb  Nb2  1  0.000  0.000  0.841  1.0
  Nb  Nb3  1  0.000  0.000  0.341  1.0
  Ni  Ni4  1  0.333  0.667  0.000  1.0
  Ni  Ni5  1  0.333  0.667  0.500  1.0
  Ni  Ni6  1  0.667  0.333  0.000  1.0
  Ni  Ni7  1  0.667  0.333  0.500  1.0
  O  O8  1  0.645  0.645  0.575  1.0
  O  O9  1  0.000  0.700  0.750  1.0
  O  O10  1  0.645  0.000  0.425  1.0
  O  O11  1  0.355  0.355  0.425  1.0
  O  O12  1  0.000  0.355  0.575  1.0
  O  O13  1  0.700  0.700  0.250  1.0
  O  O14  1  0.000  0.355  0.925  1.0
  O  O15  1  0.355  0.000  0.575  1.0
  O  O16  1  0.355  0.355  0.075  1.0
  O  O17  1  0.000  0.645  0.425  1.0
  O  O18  1  0.645  0.645  0.925  1.0
  O  O19  1  0.645  0.000  0.075  1.0
  O  O20  1  0.700  0.000  0.750  1.0
  O  O21  1  0.300  0.300  0.750  1.0
  O  O22  1  0.300  0.000  0.250  1.0
  O  O23  1  0.000  0.645  0.075  1.0
  O  O24  1  0.000  0.300  0.250  1.0
  O  O25  1  0.355  0.000  0.925  1.0
[/CIF]
.