The crystal structure described by Nb9PO25 crystallizes in the monoclinic C2 space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(3), one O(5), one O(7), one O(9), and two equivalent O(1) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and edges with two equivalent Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-32°. In the second Nb site, Nb(2) is bonded to one O(10), one O(4), one O(6), one O(8), and two equivalent O(2) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and edges with two equivalent Nb(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-32°. In the third Nb site, Nb(3) is bonded to two equivalent O(11), two equivalent O(12), and two equivalent O(13) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(11), one O(4), one O(9), and two equivalent O(7) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. In the fifth Nb site, Nb(5) is bonded to one O(10), one O(12), one O(2), one O(3), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. P(1) is bonded to two equivalent O(5) and two equivalent O(6) atoms to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 41°. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Nb(4) and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Nb(5) and two equivalent Nb(2) atoms. In the third O site, O(3) is bonded in a linear geometry to one Nb(1) and one Nb(5) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Nb(2) and one Nb(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(2) and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(5) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the eleventh O site, O(11) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the twelfth O site, O(12) is bonded in a linear geometry to one Nb(3) and one Nb(5) atom. In the thirteenth O site, O(13) is bonded in a linear geometry to two equivalent Nb(3) atoms. is represented by the CIF file [CIF]
data_Nb9PO25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.323
_cell_length_b   11.323
_cell_length_c   15.777
_cell_angle_alpha   45.835
_cell_angle_beta   45.835
_cell_angle_gamma   19.673
_symmetry_Int_Tables_number   1
_cell_volume   481.533
_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  0.666  0.673  0.443  1.0
  Nb  Nb1  1  0.327  0.334  0.557  1.0
  Nb  Nb2  1  0.893  0.882  0.783  1.0
  Nb  Nb3  1  0.118  0.107  0.217  1.0
  Nb  Nb4  1  0.958  0.042  1.000  1.0
  Nb  Nb5  1  0.898  0.883  0.328  1.0
  Nb  Nb6  1  0.117  0.102  0.672  1.0
  Nb  Nb7  1  0.777  0.787  0.109  1.0
  Nb  Nb8  1  0.213  0.223  0.891  1.0
  P  P9  1  0.751  0.249  0.500  1.0
  O  O10  1  0.855  0.836  0.510  1.0
  O  O11  1  0.164  0.145  0.490  1.0
  O  O12  1  0.636  0.652  0.201  1.0
  O  O13  1  0.348  0.364  0.799  1.0
  O  O14  1  0.709  0.729  0.291  1.0
  O  O15  1  0.271  0.291  0.709  1.0
  O  O16  1  0.002  0.978  0.729  1.0
  O  O17  1  0.022  0.998  0.271  1.0
  O  O18  1  0.583  0.516  0.516  1.0
  O  O19  1  0.484  0.417  0.484  1.0
  O  O20  1  0.903  0.967  0.614  1.0
  O  O21  1  0.033  0.097  0.386  1.0
  O  O22  1  0.623  0.604  0.635  1.0
  O  O23  1  0.396  0.377  0.365  1.0
  O  O24  1  0.744  0.760  0.861  1.0
  O  O25  1  0.240  0.256  0.139  1.0
  O  O26  1  0.798  0.760  0.396  1.0
  O  O27  1  0.240  0.202  0.604  1.0
  O  O28  1  0.808  0.842  0.954  1.0
  O  O29  1  0.158  0.192  0.046  1.0
  O  O30  1  0.946  0.949  0.169  1.0
  O  O31  1  0.051  0.054  0.831  1.0
  O  O32  1  0.879  0.889  0.063  1.0
  O  O33  1  0.111  0.121  0.937  1.0
  O  O34  1  0.487  0.513  1.000  1.0
[/CIF]
.
The crystal structure described by Nb9PO25 crystallizes in the monoclinic C2 space group. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(3), one O(5), one O(7), one O(9), and two equivalent O(1) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and edges with two equivalent Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-32°. In the second Nb site, Nb(2) is bonded to one O(10), one O(4), one O(6), one O(8), and two equivalent O(2) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and edges with two equivalent Nb(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-32°. In the third Nb site, Nb(3) is bonded to two equivalent O(11), two equivalent O(12), and two equivalent O(13) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(11), one O(4), one O(9), and two equivalent O(7) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. In the fifth Nb site, Nb(5) is bonded to one O(10), one O(12), one O(2), one O(3), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. P(1) is bonded to two equivalent O(5) and two equivalent O(6) atoms to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 41°. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Nb(4) and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Nb(5) and two equivalent Nb(2) atoms. In the third O site, O(3) is bonded in a linear geometry to one Nb(1) and one Nb(5) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Nb(2) and one Nb(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(2) and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(5) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the eleventh O site, O(11) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the twelfth O site, O(12) is bonded in a linear geometry to one Nb(3) and one Nb(5) atom. In the thirteenth O site, O(13) is bonded in a linear geometry to two equivalent Nb(3) atoms. is represented by the CIF file [CIF]
data_Nb9PO25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.323
_cell_length_b   11.323
_cell_length_c   15.777
_cell_angle_alpha   45.835
_cell_angle_beta   45.835
_cell_angle_gamma   19.673
_symmetry_Int_Tables_number   1
_cell_volume   481.533
_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  0.666  0.673  0.443  1.0
  Nb  Nb1  1  0.327  0.334  0.557  1.0
  Nb  Nb2  1  0.893  0.882  0.783  1.0
  Nb  Nb3  1  0.118  0.107  0.217  1.0
  Nb  Nb4  1  0.958  0.042  1.000  1.0
  Nb  Nb5  1  0.898  0.883  0.328  1.0
  Nb  Nb6  1  0.117  0.102  0.672  1.0
  Nb  Nb7  1  0.777  0.787  0.109  1.0
  Nb  Nb8  1  0.213  0.223  0.891  1.0
  P  P9  1  0.751  0.249  0.500  1.0
  O  O10  1  0.855  0.836  0.510  1.0
  O  O11  1  0.164  0.145  0.490  1.0
  O  O12  1  0.636  0.652  0.201  1.0
  O  O13  1  0.348  0.364  0.799  1.0
  O  O14  1  0.709  0.729  0.291  1.0
  O  O15  1  0.271  0.291  0.709  1.0
  O  O16  1  0.002  0.978  0.729  1.0
  O  O17  1  0.022  0.998  0.271  1.0
  O  O18  1  0.583  0.516  0.516  1.0
  O  O19  1  0.484  0.417  0.484  1.0
  O  O20  1  0.903  0.967  0.614  1.0
  O  O21  1  0.033  0.097  0.386  1.0
  O  O22  1  0.623  0.604  0.635  1.0
  O  O23  1  0.396  0.377  0.365  1.0
  O  O24  1  0.744  0.760  0.861  1.0
  O  O25  1  0.240  0.256  0.139  1.0
  O  O26  1  0.798  0.760  0.396  1.0
  O  O27  1  0.240  0.202  0.604  1.0
  O  O28  1  0.808  0.842  0.954  1.0
  O  O29  1  0.158  0.192  0.046  1.0
  O  O30  1  0.946  0.949  0.169  1.0
  O  O31  1  0.051  0.054  0.831  1.0
  O  O32  1  0.879  0.889  0.063  1.0
  O  O33  1  0.111  0.121  0.937  1.0
  O  O34  1  0.487  0.513  1.000  1.0
[/CIF]
.