The crystal structure described by Sb4O9 crystallizes in the monoclinic P2/m space group. There are four inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(1), one O(9), two equivalent O(3), and two equivalent O(8) atoms to form distorted SbO6 octahedra that share  a cornercorner with one Sb(3)O6 octahedra,  a cornercorner with one Sb(4)O6 octahedra, corners with two equivalent Sb(1)O6 octahedra, corners with two equivalent Sb(2)O5 trigonal bipyramids,  an edgeedge with one Sb(1)O6 octahedra, and  an edgeedge with one Sb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-29°. In the second Sb site, Sb(2) is bonded to one O(8), two equivalent O(5), and two equivalent O(6) atoms to form distorted SbO5 trigonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra, corners with two equivalent Sb(4)O6 octahedra, corners with two equivalent Sb(2)O5 trigonal bipyramids, and  an edgeedge with one Sb(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 29-74°. In the third Sb site, Sb(3) is bonded to one O(1), one O(7), two equivalent O(2), and two equivalent O(9) atoms to form a mixture of corner and edge-sharing SbO6 octahedra. The corner-sharing octahedral tilt angles range from 14-29°. In the fourth Sb site, Sb(4) is bonded to one O(1), one O(6), two equivalent O(4), and two equivalent O(7) atoms to form distorted SbO6 octahedra that share  a cornercorner with one Sb(1)O6 octahedra,  a cornercorner with one Sb(3)O6 octahedra, corners with two equivalent Sb(4)O6 octahedra, corners with two equivalent Sb(2)O5 trigonal bipyramids,  an edgeedge with one Sb(3)O6 octahedra, and  an edgeedge with one Sb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-22°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Sb(1), one Sb(3), and one Sb(4) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent Sb(3) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Sb(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Sb(4) atoms. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent Sb(2) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Sb(4) and two equivalent Sb(2) atoms. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Sb(3) and two equivalent Sb(4) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Sb(2) and two equivalent Sb(1) atoms. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Sb(1) and two equivalent Sb(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sb4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.888
_cell_length_b   9.908
_cell_length_c   10.040
_cell_angle_alpha   89.653
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   386.742
_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
  Sb  Sb0  1  0.500  0.472  0.838  1.0
  Sb  Sb1  1  0.500  0.160  0.989  1.0
  Sb  Sb2  1  0.500  0.665  0.473  1.0
  Sb  Sb3  1  0.500  0.964  0.343  1.0
  Sb  Sb4  1  0.500  0.036  0.657  1.0
  Sb  Sb5  1  0.500  0.840  0.011  1.0
  Sb  Sb6  1  0.500  0.528  0.162  1.0
  Sb  Sb7  1  0.500  0.335  0.527  1.0
  O  O8  1  0.500  0.244  0.712  1.0
  O  O9  1  0.500  0.756  0.288  1.0
  O  O10  1  0.000  0.328  0.505  1.0
  O  O11  1  0.000  0.535  0.180  1.0
  O  O12  1  0.000  0.990  0.328  1.0
  O  O13  1  0.000  0.176  0.970  1.0
  O  O14  1  0.000  0.672  0.495  1.0
  O  O15  1  0.000  0.465  0.820  1.0
  O  O16  1  0.000  0.010  0.672  1.0
  O  O17  1  0.000  0.824  0.030  1.0
  O  O18  1  0.500  0.981  0.864  1.0
  O  O19  1  0.500  0.873  0.531  1.0
  O  O20  1  0.500  0.630  0.970  1.0
  O  O21  1  0.500  0.522  0.630  1.0
  O  O22  1  0.500  0.478  0.370  1.0
  O  O23  1  0.500  0.127  0.469  1.0
  O  O24  1  0.500  0.370  0.030  1.0
  O  O25  1  0.500  0.019  0.136  1.0
[/CIF]
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The crystal structure described by Sb4O9 crystallizes in the monoclinic P2/m space group. There are four inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(1), one O(9), two equivalent O(3), and two equivalent O(8) atoms to form distorted SbO6 octahedra that share  a cornercorner with one Sb(3)O6 octahedra,  a cornercorner with one Sb(4)O6 octahedra, corners with two equivalent Sb(1)O6 octahedra, corners with two equivalent Sb(2)O5 trigonal bipyramids,  an edgeedge with one Sb(1)O6 octahedra, and  an edgeedge with one Sb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-29°. In the second Sb site, Sb(2) is bonded to one O(8), two equivalent O(5), and two equivalent O(6) atoms to form distorted SbO5 trigonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra, corners with two equivalent Sb(4)O6 octahedra, corners with two equivalent Sb(2)O5 trigonal bipyramids, and  an edgeedge with one Sb(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 29-74°. In the third Sb site, Sb(3) is bonded to one O(1), one O(7), two equivalent O(2), and two equivalent O(9) atoms to form a mixture of corner and edge-sharing SbO6 octahedra. The corner-sharing octahedral tilt angles range from 14-29°. In the fourth Sb site, Sb(4) is bonded to one O(1), one O(6), two equivalent O(4), and two equivalent O(7) atoms to form distorted SbO6 octahedra that share  a cornercorner with one Sb(1)O6 octahedra,  a cornercorner with one Sb(3)O6 octahedra, corners with two equivalent Sb(4)O6 octahedra, corners with two equivalent Sb(2)O5 trigonal bipyramids,  an edgeedge with one Sb(3)O6 octahedra, and  an edgeedge with one Sb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-22°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Sb(1), one Sb(3), and one Sb(4) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent Sb(3) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Sb(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Sb(4) atoms. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent Sb(2) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Sb(4) and two equivalent Sb(2) atoms. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Sb(3) and two equivalent Sb(4) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Sb(2) and two equivalent Sb(1) atoms. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Sb(1) and two equivalent Sb(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sb4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.888
_cell_length_b   9.908
_cell_length_c   10.040
_cell_angle_alpha   89.653
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   386.742
_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
  Sb  Sb0  1  0.500  0.472  0.838  1.0
  Sb  Sb1  1  0.500  0.160  0.989  1.0
  Sb  Sb2  1  0.500  0.665  0.473  1.0
  Sb  Sb3  1  0.500  0.964  0.343  1.0
  Sb  Sb4  1  0.500  0.036  0.657  1.0
  Sb  Sb5  1  0.500  0.840  0.011  1.0
  Sb  Sb6  1  0.500  0.528  0.162  1.0
  Sb  Sb7  1  0.500  0.335  0.527  1.0
  O  O8  1  0.500  0.244  0.712  1.0
  O  O9  1  0.500  0.756  0.288  1.0
  O  O10  1  0.000  0.328  0.505  1.0
  O  O11  1  0.000  0.535  0.180  1.0
  O  O12  1  0.000  0.990  0.328  1.0
  O  O13  1  0.000  0.176  0.970  1.0
  O  O14  1  0.000  0.672  0.495  1.0
  O  O15  1  0.000  0.465  0.820  1.0
  O  O16  1  0.000  0.010  0.672  1.0
  O  O17  1  0.000  0.824  0.030  1.0
  O  O18  1  0.500  0.981  0.864  1.0
  O  O19  1  0.500  0.873  0.531  1.0
  O  O20  1  0.500  0.630  0.970  1.0
  O  O21  1  0.500  0.522  0.630  1.0
  O  O22  1  0.500  0.478  0.370  1.0
  O  O23  1  0.500  0.127  0.469  1.0
  O  O24  1  0.500  0.370  0.030  1.0
  O  O25  1  0.500  0.019  0.136  1.0
[/CIF]
.