The structure described by Fe21O32 crystallizes in the trigonal R32 space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-60°. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(4)O4 tetrahedra, corners with five equivalent Fe(1)O4 tetrahedra,  an edgeedge with one Fe(3)O6 octahedra,  an edgeedge with one Fe(5)O6 octahedra,  an edgeedge with one Fe(6)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. In the third Fe site, Fe(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with two equivalent Fe(4)O4 tetrahedra, corners with four equivalent Fe(1)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(2) and three equivalent O(1) atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-59°. In the fifth Fe site, Fe(5) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with two equivalent Fe(4)O4 tetrahedra, corners with four equivalent Fe(1)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. In the sixth Fe site, Fe(6) is bonded to six equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Fe(1)O4 tetrahedra and edges with six equivalent Fe(2)O6 octahedra. There are six inequivalent O sites. In the first O site, O(2) is bonded to one Fe(4) and three equivalent Fe(2) atoms to form distorted corner-sharing OFe4 trigonal pyramids. In the second O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one Fe(3) atom. In the third O site, O(4) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(6), and two equivalent Fe(2) atoms. In the fourth O site, O(5) is bonded to one Fe(1), one Fe(2), one Fe(3), and one Fe(5) atom to form distorted corner-sharing OFe4 trigonal pyramids. In the fifth O site, O(6) is bonded in a trigonal planar geometry to one Fe(1), one Fe(2), and one Fe(5) atom. In the sixth O site, O(1) is bonded in a trigonal planar geometry to one Fe(3), one Fe(4), and one Fe(5) atom. is represented by the CIF card [CIF]
data_Fe21O32
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.292
_cell_length_b   8.292
_cell_length_c   8.292
_cell_angle_alpha   89.392
_cell_angle_beta   89.392
_cell_angle_gamma   89.392
_symmetry_Int_Tables_number   1
_cell_volume   570.058
_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
  Fe  Fe0  1  0.373  0.876  0.365  1.0
  Fe  Fe1  1  0.251  0.501  0.249  1.0
  Fe  Fe2  1  0.249  0.251  0.501  1.0
  Fe  Fe3  1  0.243  0.000  0.757  1.0
  Fe  Fe4  1  0.126  0.126  0.126  1.0
  Fe  Fe5  1  0.124  0.627  0.635  1.0
  Fe  Fe6  1  0.004  0.500  0.996  1.0
  Fe  Fe7  1  0.000  0.757  0.243  1.0
  Fe  Fe8  1  0.996  0.004  0.500  1.0
  Fe  Fe9  1  0.876  0.365  0.373  1.0
  Fe  Fe10  1  0.874  0.874  0.874  1.0
  Fe  Fe11  1  0.757  0.243  0.000  1.0
  Fe  Fe12  1  0.751  0.499  0.749  1.0
  Fe  Fe13  1  0.749  0.751  0.499  1.0
  Fe  Fe14  1  0.627  0.635  0.124  1.0
  Fe  Fe15  1  0.635  0.124  0.627  1.0
  Fe  Fe16  1  0.501  0.249  0.251  1.0
  Fe  Fe17  1  0.500  0.500  0.500  1.0
  Fe  Fe18  1  0.500  0.996  0.004  1.0
  Fe  Fe19  1  0.499  0.749  0.751  1.0
  Fe  Fe20  1  0.365  0.373  0.876  1.0
  O  O21  1  0.265  0.014  0.993  1.0
  O  O22  1  0.264  0.264  0.264  1.0
  O  O23  1  0.270  0.761  0.730  1.0
  O  O24  1  0.270  0.239  0.730  1.0
  O  O25  1  0.256  0.488  0.492  1.0
  O  O26  1  0.236  0.015  0.506  1.0
  O  O27  1  0.237  0.492  0.015  1.0
  O  O28  1  0.239  0.730  0.270  1.0
  O  O29  1  0.015  0.237  0.492  1.0
  O  O30  1  0.007  0.986  0.735  1.0
  O  O31  1  0.015  0.506  0.236  1.0
  O  O32  1  0.014  0.993  0.265  1.0
  O  O33  1  0.986  0.735  0.007  1.0
  O  O34  1  0.985  0.764  0.494  1.0
  O  O35  1  0.993  0.265  0.014  1.0
  O  O36  1  0.985  0.508  0.763  1.0
  O  O37  1  0.761  0.730  0.270  1.0
  O  O38  1  0.763  0.985  0.508  1.0
  O  O39  1  0.764  0.494  0.985  1.0
  O  O40  1  0.744  0.508  0.512  1.0
  O  O41  1  0.730  0.270  0.761  1.0
  O  O42  1  0.736  0.736  0.736  1.0
  O  O43  1  0.730  0.270  0.239  1.0
  O  O44  1  0.735  0.007  0.986  1.0
  O  O45  1  0.508  0.512  0.744  1.0
  O  O46  1  0.512  0.744  0.508  1.0
  O  O47  1  0.506  0.236  0.015  1.0
  O  O48  1  0.508  0.763  0.985  1.0
  O  O49  1  0.492  0.015  0.237  1.0
  O  O50  1  0.488  0.492  0.256  1.0
  O  O51  1  0.494  0.985  0.764  1.0
  O  O52  1  0.492  0.256  0.488  1.0
[/CIF]
.
The structure described by Fe21O32 crystallizes in the trigonal R32 space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-60°. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form FeO6 octahedra that share  a cornercorner with one Fe(4)O4 tetrahedra, corners with five equivalent Fe(1)O4 tetrahedra,  an edgeedge with one Fe(3)O6 octahedra,  an edgeedge with one Fe(5)O6 octahedra,  an edgeedge with one Fe(6)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. In the third Fe site, Fe(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with two equivalent Fe(4)O4 tetrahedra, corners with four equivalent Fe(1)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(2) and three equivalent O(1) atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-59°. In the fifth Fe site, Fe(5) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with two equivalent Fe(4)O4 tetrahedra, corners with four equivalent Fe(1)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. In the sixth Fe site, Fe(6) is bonded to six equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Fe(1)O4 tetrahedra and edges with six equivalent Fe(2)O6 octahedra. There are six inequivalent O sites. In the first O site, O(2) is bonded to one Fe(4) and three equivalent Fe(2) atoms to form distorted corner-sharing OFe4 trigonal pyramids. In the second O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one Fe(3) atom. In the third O site, O(4) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(6), and two equivalent Fe(2) atoms. In the fourth O site, O(5) is bonded to one Fe(1), one Fe(2), one Fe(3), and one Fe(5) atom to form distorted corner-sharing OFe4 trigonal pyramids. In the fifth O site, O(6) is bonded in a trigonal planar geometry to one Fe(1), one Fe(2), and one Fe(5) atom. In the sixth O site, O(1) is bonded in a trigonal planar geometry to one Fe(3), one Fe(4), and one Fe(5) atom. is represented by the CIF card [CIF]
data_Fe21O32
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.292
_cell_length_b   8.292
_cell_length_c   8.292
_cell_angle_alpha   89.392
_cell_angle_beta   89.392
_cell_angle_gamma   89.392
_symmetry_Int_Tables_number   1
_cell_volume   570.058
_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
  Fe  Fe0  1  0.373  0.876  0.365  1.0
  Fe  Fe1  1  0.251  0.501  0.249  1.0
  Fe  Fe2  1  0.249  0.251  0.501  1.0
  Fe  Fe3  1  0.243  0.000  0.757  1.0
  Fe  Fe4  1  0.126  0.126  0.126  1.0
  Fe  Fe5  1  0.124  0.627  0.635  1.0
  Fe  Fe6  1  0.004  0.500  0.996  1.0
  Fe  Fe7  1  0.000  0.757  0.243  1.0
  Fe  Fe8  1  0.996  0.004  0.500  1.0
  Fe  Fe9  1  0.876  0.365  0.373  1.0
  Fe  Fe10  1  0.874  0.874  0.874  1.0
  Fe  Fe11  1  0.757  0.243  0.000  1.0
  Fe  Fe12  1  0.751  0.499  0.749  1.0
  Fe  Fe13  1  0.749  0.751  0.499  1.0
  Fe  Fe14  1  0.627  0.635  0.124  1.0
  Fe  Fe15  1  0.635  0.124  0.627  1.0
  Fe  Fe16  1  0.501  0.249  0.251  1.0
  Fe  Fe17  1  0.500  0.500  0.500  1.0
  Fe  Fe18  1  0.500  0.996  0.004  1.0
  Fe  Fe19  1  0.499  0.749  0.751  1.0
  Fe  Fe20  1  0.365  0.373  0.876  1.0
  O  O21  1  0.265  0.014  0.993  1.0
  O  O22  1  0.264  0.264  0.264  1.0
  O  O23  1  0.270  0.761  0.730  1.0
  O  O24  1  0.270  0.239  0.730  1.0
  O  O25  1  0.256  0.488  0.492  1.0
  O  O26  1  0.236  0.015  0.506  1.0
  O  O27  1  0.237  0.492  0.015  1.0
  O  O28  1  0.239  0.730  0.270  1.0
  O  O29  1  0.015  0.237  0.492  1.0
  O  O30  1  0.007  0.986  0.735  1.0
  O  O31  1  0.015  0.506  0.236  1.0
  O  O32  1  0.014  0.993  0.265  1.0
  O  O33  1  0.986  0.735  0.007  1.0
  O  O34  1  0.985  0.764  0.494  1.0
  O  O35  1  0.993  0.265  0.014  1.0
  O  O36  1  0.985  0.508  0.763  1.0
  O  O37  1  0.761  0.730  0.270  1.0
  O  O38  1  0.763  0.985  0.508  1.0
  O  O39  1  0.764  0.494  0.985  1.0
  O  O40  1  0.744  0.508  0.512  1.0
  O  O41  1  0.730  0.270  0.761  1.0
  O  O42  1  0.736  0.736  0.736  1.0
  O  O43  1  0.730  0.270  0.239  1.0
  O  O44  1  0.735  0.007  0.986  1.0
  O  O45  1  0.508  0.512  0.744  1.0
  O  O46  1  0.512  0.744  0.508  1.0
  O  O47  1  0.506  0.236  0.015  1.0
  O  O48  1  0.508  0.763  0.985  1.0
  O  O49  1  0.492  0.015  0.237  1.0
  O  O50  1  0.488  0.492  0.256  1.0
  O  O51  1  0.494  0.985  0.764  1.0
  O  O52  1  0.492  0.256  0.488  1.0
[/CIF]
.