The structure described by NiCr2O4 is Spinel structured and crystallizes in the triclinic P1 space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(3), one O(4), one O(6), one O(7), and one O(8) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(2)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the third Cr site, Cr(3) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(8) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the fourth Cr site, Cr(4) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(7) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(3)O6 octahedra. 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), and one O(8) atom to form NiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with three equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-62°. In the second Ni site, Ni(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form NiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with three equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-61°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Cr(2), one Cr(3), one Cr(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Cr(1), one Cr(3), one Cr(4), and one Ni(1) atom. In the third O site, O(3) is bonded to one Cr(1), one Cr(2), one Cr(4), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the fourth O site, O(4) is bonded to one Cr(1), one Cr(2), one Cr(3), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Cr(2), one Cr(3), one Cr(4), and one Ni(1) atom. In the sixth O site, O(6) is bonded to one Cr(1), one Cr(3), one Cr(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the seventh O site, O(7) is bonded to one Cr(1), one Cr(2), one Cr(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the eighth O site, O(8) is bonded to one Cr(1), one Cr(2), one Cr(3), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. is represented by the CIF file [CIF]
data_Cr2NiO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.952
_cell_length_b   5.991
_cell_length_c   5.965
_cell_angle_alpha   60.853
_cell_angle_beta   60.087
_cell_angle_gamma   90.105
_symmetry_Int_Tables_number   1
_cell_volume   152.366
_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
  Cr  Cr0  1  1.000  0.001  0.499  1.0
  Cr  Cr1  1  0.000  0.500  1.000  1.0
  Cr  Cr2  1  0.000  0.000  0.000  1.0
  Cr  Cr3  1  0.499  1.000  0.501  1.0
  Ni  Ni4  1  0.628  0.381  0.749  1.0
  Ni  Ni5  1  0.377  0.620  0.251  1.0
  O  O6  1  0.242  0.762  0.976  1.0
  O  O7  1  0.762  0.788  0.471  1.0
  O  O8  1  0.761  0.242  0.477  1.0
  O  O9  1  0.785  0.765  0.972  1.0
  O  O10  1  0.756  0.234  0.028  1.0
  O  O11  1  0.234  0.212  0.529  1.0
  O  O12  1  0.237  0.758  0.524  1.0
  O  O13  1  0.218  0.238  0.024  1.0
[/CIF]
.
The structure described by NiCr2O4 is Spinel structured and crystallizes in the triclinic P1 space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(3), one O(4), one O(6), one O(7), and one O(8) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(2)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the third Cr site, Cr(3) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(8) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the fourth Cr site, Cr(4) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(7) atom to form CrO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(3)O6 octahedra. 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), and one O(8) atom to form NiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with three equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-62°. In the second Ni site, Ni(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form NiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with three equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-61°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Cr(2), one Cr(3), one Cr(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Cr(1), one Cr(3), one Cr(4), and one Ni(1) atom. In the third O site, O(3) is bonded to one Cr(1), one Cr(2), one Cr(4), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the fourth O site, O(4) is bonded to one Cr(1), one Cr(2), one Cr(3), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Cr(2), one Cr(3), one Cr(4), and one Ni(1) atom. In the sixth O site, O(6) is bonded to one Cr(1), one Cr(3), one Cr(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the seventh O site, O(7) is bonded to one Cr(1), one Cr(2), one Cr(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. In the eighth O site, O(8) is bonded to one Cr(1), one Cr(2), one Cr(3), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing OCr3Ni trigonal pyramids. is represented by the CIF file [CIF]
data_Cr2NiO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.952
_cell_length_b   5.991
_cell_length_c   5.965
_cell_angle_alpha   60.853
_cell_angle_beta   60.087
_cell_angle_gamma   90.105
_symmetry_Int_Tables_number   1
_cell_volume   152.366
_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
  Cr  Cr0  1  1.000  0.001  0.499  1.0
  Cr  Cr1  1  0.000  0.500  1.000  1.0
  Cr  Cr2  1  0.000  0.000  0.000  1.0
  Cr  Cr3  1  0.499  1.000  0.501  1.0
  Ni  Ni4  1  0.628  0.381  0.749  1.0
  Ni  Ni5  1  0.377  0.620  0.251  1.0
  O  O6  1  0.242  0.762  0.976  1.0
  O  O7  1  0.762  0.788  0.471  1.0
  O  O8  1  0.761  0.242  0.477  1.0
  O  O9  1  0.785  0.765  0.972  1.0
  O  O10  1  0.756  0.234  0.028  1.0
  O  O11  1  0.234  0.212  0.529  1.0
  O  O12  1  0.237  0.758  0.524  1.0
  O  O13  1  0.218  0.238  0.024  1.0
[/CIF]
.