The structure described by Ba8Fe8O21 crystallizes in the triclinic P-1 space group. There are five inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 1-coordinate geometry to one O(2), one O(7), and two equivalent O(1) atoms. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to two equivalent Fe(1), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the third Ba site, Ba(3) is bonded in a 2-coordinate geometry to two equivalent O(11) and two equivalent O(12) atoms. In the fourth Ba site, Ba(4) is bonded in a 2-coordinate geometry to one O(11), one O(7), and two equivalent O(12) atoms. In the fifth Ba site, Ba(5) is bonded in a 2-coordinate geometry to one O(1), one O(12), and two equivalent O(7) atoms. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 5-coordinate geometry to one Ba(2), one O(1), one O(2), one O(3), one O(4), and one O(5) atom. In the second Fe site, Fe(2) is bonded in a 1-coordinate geometry to one O(12), one O(13), one O(6), one O(7), and one O(9) atom. In the third Fe site, Fe(3) is bonded in a distorted linear geometry to one O(1), one O(5), one O(6), one O(7), and one O(9) atom. In the fourth Fe site, Fe(4) is bonded in a 1-coordinate geometry to one O(10), one O(11), one O(12), one O(13), and one O(8) atom. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a 1-coordinate geometry to one Ba(2) and one Fe(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Ba(2) and two equivalent Fe(1) atoms. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Fe(1) and one Fe(3) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Fe(2) and one Fe(3) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom. In the eighth O site, O(8) is bonded in a linear geometry to two equivalent Fe(4) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Fe(2) and one Fe(3) atom. In the tenth O site, O(10) is bonded in a distorted linear geometry to two equivalent Fe(4) atoms. In the eleventh O site, O(11) is bonded in a 6-coordinate geometry to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms. In the twelfth O site, O(12) is bonded to one Ba(3), one Ba(5), two equivalent Ba(4), one Fe(2), and one Fe(4) atom to form distorted corner-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the thirteenth O site, O(13) is bonded in a 2-coordinate geometry to one Fe(2) and one Fe(4) atom. is represented by the CIF file [CIF]
data_Ba8Fe8O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.744
_cell_length_b   5.783
_cell_length_c   19.040
_cell_angle_alpha   97.622
_cell_angle_beta   90.666
_cell_angle_gamma   119.396
_symmetry_Int_Tables_number   1
_cell_volume   544.042
_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
  Ba  Ba0  1  0.620  0.997  0.127  1.0
  Ba  Ba1  1  0.500  0.500  0.000  1.0
  Ba  Ba2  1  0.380  0.003  0.873  1.0
  Ba  Ba3  1  0.000  0.500  0.500  1.0
  Ba  Ba4  1  0.876  0.996  0.372  1.0
  Ba  Ba5  1  0.754  0.502  0.246  1.0
  Ba  Ba6  1  0.246  0.498  0.754  1.0
  Ba  Ba7  1  0.124  0.004  0.628  1.0
  Fe  Fe8  1  0.996  0.284  0.931  1.0
  Fe  Fe9  1  0.298  0.707  0.304  1.0
  Fe  Fe10  1  0.004  0.716  0.069  1.0
  Fe  Fe11  1  0.171  0.236  0.186  1.0
  Fe  Fe12  1  0.702  0.293  0.696  1.0
  Fe  Fe13  1  0.442  0.271  0.444  1.0
  Fe  Fe14  1  0.558  0.729  0.556  1.0
  Fe  Fe15  1  0.829  0.764  0.814  1.0
  O  O16  1  0.402  0.521  0.873  1.0
  O  O17  1  0.000  0.000  0.000  1.0
  O  O18  1  0.859  0.475  0.883  1.0
  O  O19  1  0.000  0.500  0.000  1.0
  O  O20  1  0.122  0.993  0.123  1.0
  O  O21  1  0.878  0.007  0.877  1.0
  O  O22  1  0.248  0.988  0.259  1.0
  O  O23  1  0.141  0.525  0.117  1.0
  O  O24  1  0.740  0.993  0.251  1.0
  O  O25  1  0.598  0.479  0.127  1.0
  O  O26  1  0.500  0.500  0.500  1.0
  O  O27  1  0.236  0.479  0.247  1.0
  O  O28  1  0.500  0.000  0.500  1.0
  O  O29  1  0.000  0.000  0.500  1.0
  O  O30  1  0.139  0.520  0.624  1.0
  O  O31  1  0.861  0.480  0.376  1.0
  O  O32  1  0.370  0.495  0.374  1.0
  O  O33  1  0.630  0.505  0.626  1.0
  O  O34  1  0.764  0.521  0.753  1.0
  O  O35  1  0.260  0.007  0.749  1.0
  O  O36  1  0.752  0.012  0.741  1.0
[/CIF]
.
The structure described by Ba8Fe8O21 crystallizes in the triclinic P-1 space group. There are five inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 1-coordinate geometry to one O(2), one O(7), and two equivalent O(1) atoms. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to two equivalent Fe(1), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the third Ba site, Ba(3) is bonded in a 2-coordinate geometry to two equivalent O(11) and two equivalent O(12) atoms. In the fourth Ba site, Ba(4) is bonded in a 2-coordinate geometry to one O(11), one O(7), and two equivalent O(12) atoms. In the fifth Ba site, Ba(5) is bonded in a 2-coordinate geometry to one O(1), one O(12), and two equivalent O(7) atoms. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 5-coordinate geometry to one Ba(2), one O(1), one O(2), one O(3), one O(4), and one O(5) atom. In the second Fe site, Fe(2) is bonded in a 1-coordinate geometry to one O(12), one O(13), one O(6), one O(7), and one O(9) atom. In the third Fe site, Fe(3) is bonded in a distorted linear geometry to one O(1), one O(5), one O(6), one O(7), and one O(9) atom. In the fourth Fe site, Fe(4) is bonded in a 1-coordinate geometry to one O(10), one O(11), one O(12), one O(13), and one O(8) atom. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(1), one Fe(1), and one Fe(3) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a 1-coordinate geometry to one Ba(2) and one Fe(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Ba(2) and two equivalent Fe(1) atoms. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Fe(1) and one Fe(3) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Fe(2) and one Fe(3) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Fe(2), and one Fe(3) atom. In the eighth O site, O(8) is bonded in a linear geometry to two equivalent Fe(4) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Fe(2) and one Fe(3) atom. In the tenth O site, O(10) is bonded in a distorted linear geometry to two equivalent Fe(4) atoms. In the eleventh O site, O(11) is bonded in a 6-coordinate geometry to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Fe(4) atoms. In the twelfth O site, O(12) is bonded to one Ba(3), one Ba(5), two equivalent Ba(4), one Fe(2), and one Fe(4) atom to form distorted corner-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the thirteenth O site, O(13) is bonded in a 2-coordinate geometry to one Fe(2) and one Fe(4) atom. is represented by the CIF file [CIF]
data_Ba8Fe8O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.744
_cell_length_b   5.783
_cell_length_c   19.040
_cell_angle_alpha   97.622
_cell_angle_beta   90.666
_cell_angle_gamma   119.396
_symmetry_Int_Tables_number   1
_cell_volume   544.042
_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
  Ba  Ba0  1  0.620  0.997  0.127  1.0
  Ba  Ba1  1  0.500  0.500  0.000  1.0
  Ba  Ba2  1  0.380  0.003  0.873  1.0
  Ba  Ba3  1  0.000  0.500  0.500  1.0
  Ba  Ba4  1  0.876  0.996  0.372  1.0
  Ba  Ba5  1  0.754  0.502  0.246  1.0
  Ba  Ba6  1  0.246  0.498  0.754  1.0
  Ba  Ba7  1  0.124  0.004  0.628  1.0
  Fe  Fe8  1  0.996  0.284  0.931  1.0
  Fe  Fe9  1  0.298  0.707  0.304  1.0
  Fe  Fe10  1  0.004  0.716  0.069  1.0
  Fe  Fe11  1  0.171  0.236  0.186  1.0
  Fe  Fe12  1  0.702  0.293  0.696  1.0
  Fe  Fe13  1  0.442  0.271  0.444  1.0
  Fe  Fe14  1  0.558  0.729  0.556  1.0
  Fe  Fe15  1  0.829  0.764  0.814  1.0
  O  O16  1  0.402  0.521  0.873  1.0
  O  O17  1  0.000  0.000  0.000  1.0
  O  O18  1  0.859  0.475  0.883  1.0
  O  O19  1  0.000  0.500  0.000  1.0
  O  O20  1  0.122  0.993  0.123  1.0
  O  O21  1  0.878  0.007  0.877  1.0
  O  O22  1  0.248  0.988  0.259  1.0
  O  O23  1  0.141  0.525  0.117  1.0
  O  O24  1  0.740  0.993  0.251  1.0
  O  O25  1  0.598  0.479  0.127  1.0
  O  O26  1  0.500  0.500  0.500  1.0
  O  O27  1  0.236  0.479  0.247  1.0
  O  O28  1  0.500  0.000  0.500  1.0
  O  O29  1  0.000  0.000  0.500  1.0
  O  O30  1  0.139  0.520  0.624  1.0
  O  O31  1  0.861  0.480  0.376  1.0
  O  O32  1  0.370  0.495  0.374  1.0
  O  O33  1  0.630  0.505  0.626  1.0
  O  O34  1  0.764  0.521  0.753  1.0
  O  O35  1  0.260  0.007  0.749  1.0
  O  O36  1  0.752  0.012  0.741  1.0
[/CIF]
.