The crystal structure described by Cr8O21 crystallizes in the triclinic P-1 space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(10), one O(3), one O(5), and one O(8) atom to form distorted corner-sharing CrO4 tetrahedra. In the second Cr site, Cr(2) is bonded in a distorted hexagonal planar geometry to one O(11), one O(4), one O(6), one O(7), and two equivalent O(1) atoms. In the third Cr site, Cr(3) is bonded to one O(3), one O(6), one O(7), and one O(9) atom to form distorted corner-sharing CrO4 tetrahedra. In the fourth Cr site, Cr(4) is bonded in a distorted tetrahedral geometry to one O(1), one O(11), one O(2), and one O(4) atom. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cr(4) and two equivalent Cr(2) atoms. In the second O site, O(2) is bonded in a single-bond geometry to one Cr(4) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one Cr(3) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(4) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Cr(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one Cr(1) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one Cr(3) atom. In the tenth O site, O(10) is bonded in a linear geometry to two equivalent Cr(1) atoms. In the eleventh O site, O(11) is bonded in a linear geometry to one Cr(2) and one Cr(4) atom. is represented by the CIF file [CIF]
data_Cr8O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.458
_cell_length_b   6.748
_cell_length_c   12.889
_cell_angle_alpha   105.035
_cell_angle_beta   87.482
_cell_angle_gamma   102.918
_symmetry_Int_Tables_number   1
_cell_volume   446.872
_cell_formula_units_Z   1
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  0.735  0.206  0.528  1.0
  Cr  Cr1  1  0.859  0.786  0.074  1.0
  Cr  Cr2  1  0.653  0.362  0.749  1.0
  Cr  Cr3  1  0.300  0.766  0.904  1.0
  Cr  Cr4  1  0.700  0.234  0.096  1.0
  Cr  Cr5  1  0.141  0.214  0.926  1.0
  Cr  Cr6  1  0.347  0.638  0.251  1.0
  Cr  Cr7  1  0.265  0.794  0.472  1.0
  O  O8  1  0.909  0.102  0.055  1.0
  O  O9  1  0.634  0.131  0.220  1.0
  O  O10  1  0.375  0.679  0.382  1.0
  O  O11  1  0.832  0.489  0.077  1.0
  O  O12  1  0.023  0.881  0.422  1.0
  O  O13  1  0.369  0.290  0.803  1.0
  O  O14  1  0.847  0.224  0.826  1.0
  O  O15  1  0.189  0.618  0.581  1.0
  O  O16  1  0.153  0.776  0.174  1.0
  O  O17  1  0.761  0.605  0.741  1.0
  O  O18  1  0.625  0.321  0.618  1.0
  O  O19  1  0.500  0.000  0.500  1.0
  O  O20  1  0.437  0.204  0.023  1.0
  O  O21  1  0.631  0.710  0.197  1.0
  O  O22  1  0.811  0.382  0.419  1.0
  O  O23  1  0.239  0.395  0.259  1.0
  O  O24  1  0.168  0.511  0.923  1.0
  O  O25  1  0.977  0.119  0.578  1.0
  O  O26  1  0.366  0.869  0.780  1.0
  O  O27  1  0.563  0.796  0.977  1.0
  O  O28  1  0.091  0.898  0.945  1.0
[/CIF]
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The crystal structure described by Cr8O21 crystallizes in the triclinic P-1 space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(10), one O(3), one O(5), and one O(8) atom to form distorted corner-sharing CrO4 tetrahedra. In the second Cr site, Cr(2) is bonded in a distorted hexagonal planar geometry to one O(11), one O(4), one O(6), one O(7), and two equivalent O(1) atoms. In the third Cr site, Cr(3) is bonded to one O(3), one O(6), one O(7), and one O(9) atom to form distorted corner-sharing CrO4 tetrahedra. In the fourth Cr site, Cr(4) is bonded in a distorted tetrahedral geometry to one O(1), one O(11), one O(2), and one O(4) atom. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cr(4) and two equivalent Cr(2) atoms. In the second O site, O(2) is bonded in a single-bond geometry to one Cr(4) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one Cr(3) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(4) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Cr(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one Cr(1) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one Cr(3) atom. In the tenth O site, O(10) is bonded in a linear geometry to two equivalent Cr(1) atoms. In the eleventh O site, O(11) is bonded in a linear geometry to one Cr(2) and one Cr(4) atom. is represented by the CIF file [CIF]
data_Cr8O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.458
_cell_length_b   6.748
_cell_length_c   12.889
_cell_angle_alpha   105.035
_cell_angle_beta   87.482
_cell_angle_gamma   102.918
_symmetry_Int_Tables_number   1
_cell_volume   446.872
_cell_formula_units_Z   1
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  0.735  0.206  0.528  1.0
  Cr  Cr1  1  0.859  0.786  0.074  1.0
  Cr  Cr2  1  0.653  0.362  0.749  1.0
  Cr  Cr3  1  0.300  0.766  0.904  1.0
  Cr  Cr4  1  0.700  0.234  0.096  1.0
  Cr  Cr5  1  0.141  0.214  0.926  1.0
  Cr  Cr6  1  0.347  0.638  0.251  1.0
  Cr  Cr7  1  0.265  0.794  0.472  1.0
  O  O8  1  0.909  0.102  0.055  1.0
  O  O9  1  0.634  0.131  0.220  1.0
  O  O10  1  0.375  0.679  0.382  1.0
  O  O11  1  0.832  0.489  0.077  1.0
  O  O12  1  0.023  0.881  0.422  1.0
  O  O13  1  0.369  0.290  0.803  1.0
  O  O14  1  0.847  0.224  0.826  1.0
  O  O15  1  0.189  0.618  0.581  1.0
  O  O16  1  0.153  0.776  0.174  1.0
  O  O17  1  0.761  0.605  0.741  1.0
  O  O18  1  0.625  0.321  0.618  1.0
  O  O19  1  0.500  0.000  0.500  1.0
  O  O20  1  0.437  0.204  0.023  1.0
  O  O21  1  0.631  0.710  0.197  1.0
  O  O22  1  0.811  0.382  0.419  1.0
  O  O23  1  0.239  0.395  0.259  1.0
  O  O24  1  0.168  0.511  0.923  1.0
  O  O25  1  0.977  0.119  0.578  1.0
  O  O26  1  0.366  0.869  0.780  1.0
  O  O27  1  0.563  0.796  0.977  1.0
  O  O28  1  0.091  0.898  0.945  1.0
[/CIF]
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