The structure described by Nb4O9 crystallizes in the triclinic P1 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(5), one O(7), and one O(8) atom to form distorted NbO5 square pyramids that share corners with four equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(3)O5 square pyramid, and corners with two equivalent Nb(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 16-58°. In the second Nb site, Nb(2) is bonded to one O(1), one O(3), one O(5), one O(6), and one O(9) atom to form NbO5 square pyramids that share corners with two equivalent Nb(1)O5 square pyramids, corners with three equivalent Nb(3)O5 square pyramids, and  an edgeedge with one Nb(4)O6 octahedra. In the third Nb site, Nb(3) is bonded to one O(2), one O(3), one O(4), one O(6), and one O(9) atom to form NbO5 square pyramids that share corners with three equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(1)O5 square pyramid, and corners with three equivalent Nb(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 38-53°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form a mixture of distorted corner and edge-sharing NbO6 octahedra. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Nb(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Nb(4) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Nb(2), one Nb(3), and one Nb(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Nb(3) and one Nb(4) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Nb(1) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(3) atom. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(4) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nb4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.058
_cell_length_b   5.622
_cell_length_c   6.972
_cell_angle_alpha   105.178
_cell_angle_beta   109.585
_cell_angle_gamma   91.135
_symmetry_Int_Tables_number   1
_cell_volume   179.002
_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
  Nb  Nb0  1  0.369  0.263  0.279  1.0
  Nb  Nb1  1  0.149  0.214  0.733  1.0
  Nb  Nb2  1  0.608  0.726  0.700  1.0
  Nb  Nb3  1  0.891  0.758  0.268  1.0
  O  O4  1  0.133  0.127  0.410  1.0
  O  O5  1  0.257  0.645  0.408  1.0
  O  O6  1  0.868  0.876  0.595  1.0
  O  O7  1  0.870  0.726  0.979  1.0
  O  O8  1  0.099  0.260  1.000  1.0
  O  O9  1  0.330  0.522  0.769  1.0
  O  O10  1  0.574  0.994  0.242  1.0
  O  O11  1  0.662  0.481  0.237  1.0
  O  O12  1  0.463  0.035  0.789  1.0
[/CIF]
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The structure described by Nb4O9 crystallizes in the triclinic P1 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(5), one O(7), and one O(8) atom to form distorted NbO5 square pyramids that share corners with four equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(3)O5 square pyramid, and corners with two equivalent Nb(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 16-58°. In the second Nb site, Nb(2) is bonded to one O(1), one O(3), one O(5), one O(6), and one O(9) atom to form NbO5 square pyramids that share corners with two equivalent Nb(1)O5 square pyramids, corners with three equivalent Nb(3)O5 square pyramids, and  an edgeedge with one Nb(4)O6 octahedra. In the third Nb site, Nb(3) is bonded to one O(2), one O(3), one O(4), one O(6), and one O(9) atom to form NbO5 square pyramids that share corners with three equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(1)O5 square pyramid, and corners with three equivalent Nb(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 38-53°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form a mixture of distorted corner and edge-sharing NbO6 octahedra. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Nb(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Nb(4) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Nb(2), one Nb(3), and one Nb(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Nb(3) and one Nb(4) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Nb(1) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(3) atom. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(4) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nb4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.058
_cell_length_b   5.622
_cell_length_c   6.972
_cell_angle_alpha   105.178
_cell_angle_beta   109.585
_cell_angle_gamma   91.135
_symmetry_Int_Tables_number   1
_cell_volume   179.002
_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
  Nb  Nb0  1  0.369  0.263  0.279  1.0
  Nb  Nb1  1  0.149  0.214  0.733  1.0
  Nb  Nb2  1  0.608  0.726  0.700  1.0
  Nb  Nb3  1  0.891  0.758  0.268  1.0
  O  O4  1  0.133  0.127  0.410  1.0
  O  O5  1  0.257  0.645  0.408  1.0
  O  O6  1  0.868  0.876  0.595  1.0
  O  O7  1  0.870  0.726  0.979  1.0
  O  O8  1  0.099  0.260  1.000  1.0
  O  O9  1  0.330  0.522  0.769  1.0
  O  O10  1  0.574  0.994  0.242  1.0
  O  O11  1  0.662  0.481  0.237  1.0
  O  O12  1  0.463  0.035  0.789  1.0
[/CIF]
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