The material described by ZnCr2O4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form CrO6 octahedra that share corners with three equivalent Zn(1)O6 pentagonal pyramids, edges with two equivalent Cr(1)O6 octahedra, edges with four equivalent Cr(2)O6 octahedra, and  an edgeedge with one Zn(1)O6 pentagonal pyramid. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share edges with two equivalent Cr(2)O6 octahedra, edges with four equivalent Cr(1)O6 octahedra, and edges with two equivalent Zn(1)O6 pentagonal pyramids. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted ZnO6 pentagonal pyramids that share corners with six equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-18°. In the second Zn site, Zn(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Zn(1) atom. In the second O site, O(2) is bonded to one Cr(1), two equivalent Cr(2), and one Zn(2) atom to form OZnCr3 trigonal pyramids that share corners with four equivalent O(3)Zn2Cr3 trigonal bipyramids, corners with three equivalent O(2)ZnCr3 trigonal pyramids, and edges with four equivalent O(3)Zn2Cr3 trigonal bipyramids. In the third O site, O(3) is bonded to one Cr(2), two equivalent Cr(1), one Zn(1), and one Zn(2) atom to form OZn2Cr3 trigonal bipyramids that share corners with five equivalent O(3)Zn2Cr3 trigonal bipyramids, corners with two equivalent O(2)ZnCr3 trigonal pyramids, edges with four equivalent O(3)Zn2Cr3 trigonal bipyramids, and edges with two equivalent O(2)ZnCr3 trigonal pyramids. is represented by the CIF file [CIF]
data_ZnCr2O4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.114
_cell_length_b   5.929
_cell_length_c   10.268
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   311.346
_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
  Zn  Zn0  1  0.365  0.000  0.500  1.0
  Zn  Zn1  1  0.635  0.500  0.000  1.0
  Zn  Zn2  1  0.042  0.000  0.000  1.0
  Zn  Zn3  1  0.958  0.500  0.500  1.0
  Cr  Cr4  1  0.010  0.500  0.237  1.0
  Cr  Cr5  1  0.010  0.500  0.763  1.0
  Cr  Cr6  1  0.990  0.000  0.263  1.0
  Cr  Cr7  1  0.990  0.000  0.737  1.0
  Cr  Cr8  1  0.500  0.250  0.250  1.0
  Cr  Cr9  1  0.500  0.750  0.750  1.0
  Cr  Cr10  1  0.500  0.750  0.250  1.0
  Cr  Cr11  1  0.500  0.250  0.750  1.0
  O  O12  1  0.356  0.500  0.144  1.0
  O  O13  1  0.356  0.500  0.856  1.0
  O  O14  1  0.644  0.000  0.356  1.0
  O  O15  1  0.644  0.000  0.644  1.0
  O  O16  1  0.690  0.500  0.348  1.0
  O  O17  1  0.690  0.500  0.652  1.0
  O  O18  1  0.310  0.000  0.152  1.0
  O  O19  1  0.310  0.000  0.848  1.0
  O  O20  1  0.166  0.252  0.359  1.0
  O  O21  1  0.166  0.748  0.641  1.0
  O  O22  1  0.834  0.752  0.141  1.0
  O  O23  1  0.834  0.248  0.859  1.0
  O  O24  1  0.834  0.248  0.141  1.0
  O  O25  1  0.834  0.752  0.859  1.0
  O  O26  1  0.166  0.748  0.359  1.0
  O  O27  1  0.166  0.252  0.641  1.0
[/CIF]
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The material described by ZnCr2O4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form CrO6 octahedra that share corners with three equivalent Zn(1)O6 pentagonal pyramids, edges with two equivalent Cr(1)O6 octahedra, edges with four equivalent Cr(2)O6 octahedra, and  an edgeedge with one Zn(1)O6 pentagonal pyramid. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share edges with two equivalent Cr(2)O6 octahedra, edges with four equivalent Cr(1)O6 octahedra, and edges with two equivalent Zn(1)O6 pentagonal pyramids. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted ZnO6 pentagonal pyramids that share corners with six equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-18°. In the second Zn site, Zn(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Zn(1) atom. In the second O site, O(2) is bonded to one Cr(1), two equivalent Cr(2), and one Zn(2) atom to form OZnCr3 trigonal pyramids that share corners with four equivalent O(3)Zn2Cr3 trigonal bipyramids, corners with three equivalent O(2)ZnCr3 trigonal pyramids, and edges with four equivalent O(3)Zn2Cr3 trigonal bipyramids. In the third O site, O(3) is bonded to one Cr(2), two equivalent Cr(1), one Zn(1), and one Zn(2) atom to form OZn2Cr3 trigonal bipyramids that share corners with five equivalent O(3)Zn2Cr3 trigonal bipyramids, corners with two equivalent O(2)ZnCr3 trigonal pyramids, edges with four equivalent O(3)Zn2Cr3 trigonal bipyramids, and edges with two equivalent O(2)ZnCr3 trigonal pyramids. is represented by the CIF file [CIF]
data_ZnCr2O4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.114
_cell_length_b   5.929
_cell_length_c   10.268
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   311.346
_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
  Zn  Zn0  1  0.365  0.000  0.500  1.0
  Zn  Zn1  1  0.635  0.500  0.000  1.0
  Zn  Zn2  1  0.042  0.000  0.000  1.0
  Zn  Zn3  1  0.958  0.500  0.500  1.0
  Cr  Cr4  1  0.010  0.500  0.237  1.0
  Cr  Cr5  1  0.010  0.500  0.763  1.0
  Cr  Cr6  1  0.990  0.000  0.263  1.0
  Cr  Cr7  1  0.990  0.000  0.737  1.0
  Cr  Cr8  1  0.500  0.250  0.250  1.0
  Cr  Cr9  1  0.500  0.750  0.750  1.0
  Cr  Cr10  1  0.500  0.750  0.250  1.0
  Cr  Cr11  1  0.500  0.250  0.750  1.0
  O  O12  1  0.356  0.500  0.144  1.0
  O  O13  1  0.356  0.500  0.856  1.0
  O  O14  1  0.644  0.000  0.356  1.0
  O  O15  1  0.644  0.000  0.644  1.0
  O  O16  1  0.690  0.500  0.348  1.0
  O  O17  1  0.690  0.500  0.652  1.0
  O  O18  1  0.310  0.000  0.152  1.0
  O  O19  1  0.310  0.000  0.848  1.0
  O  O20  1  0.166  0.252  0.359  1.0
  O  O21  1  0.166  0.748  0.641  1.0
  O  O22  1  0.834  0.752  0.141  1.0
  O  O23  1  0.834  0.248  0.859  1.0
  O  O24  1  0.834  0.248  0.141  1.0
  O  O25  1  0.834  0.752  0.859  1.0
  O  O26  1  0.166  0.748  0.359  1.0
  O  O27  1  0.166  0.252  0.641  1.0
[/CIF]
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