The crystal structure described by Nb9AsO25 crystallizes in the monoclinic C2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(6), one O(8), and two equivalent O(12) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 4-31°. In the second Nb site, Nb(2) is bonded to one O(11), one O(4), one O(7), one O(9), and two equivalent O(13) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 4-31°. In the third Nb site, Nb(3) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fourth Nb site, Nb(4,5) is bonded to one O(1), one O(13), one O(7), one O(8), and two equivalent O(11) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra;  a cornercorner with one Nb(2)O6 octahedra; corners with two equivalent Nb(4,5)O6 octahedra;  a cornercorner with one As(1)O4 tetrahedra; and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-32°. As(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form AsO4 tetrahedra that share corners with four equivalent Nb(4,5)O6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are thirteen inequivalent O sites. In the first O site, O(8) is bonded in a linear geometry to one Nb(1) and one Nb(4,5) atom. In the second O site, O(9) is bonded in a linear geometry to one Nb(2) and one Nb(4,5) atom. In the third O site, O(10) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(4,5) atoms. In the fourth O site, O(11) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(4,5) atoms. In the fifth O site, O(12) is bonded in a 3-coordinate geometry to one Nb(4,5) and two equivalent Nb(1) atoms. In the sixth O site, O(13) is bonded in a 3-coordinate geometry to one Nb(4,5) and two equivalent Nb(2) atoms. In the seventh O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Nb(4,5) and one As(1) atom. In the eighth O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Nb(4,5) and one As(1) atom. In the ninth O site, O(3) is bonded in a linear geometry to one Nb(1) and one Nb(3) atom. In the tenth O site, O(4) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the eleventh O site, O(5) is bonded in a linear geometry to two equivalent Nb(3) atoms. In the twelfth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(4,5) atom. In the thirteenth O site, O(7) is bonded in a linear geometry to one Nb(2) and one Nb(4,5) atom. is represented by the CIF card [CIF]
data_Nb9AsO25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.383
_cell_length_b   11.383
_cell_length_c   15.865
_cell_angle_alpha   45.825
_cell_angle_beta   45.825
_cell_angle_gamma   19.547
_symmetry_Int_Tables_number   1
_cell_volume   486.355
_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  0.784  0.779  0.326  1.0
  Nb  Nb1  1  0.221  0.216  0.674  1.0
  Nb  Nb2  1  0.107  0.108  0.111  1.0
  Nb  Nb3  1  0.892  0.893  0.889  1.0
  Nb  Nb4  1  0.960  0.040  1.000  1.0
  Nb  Nb5  1  0.681  0.665  0.212  1.0
  Nb  Nb6  1  0.335  0.319  0.788  1.0
  Nb  Nb7  1  0.877  0.892  0.442  1.0
  Nb  Nb8  1  0.108  0.123  0.558  1.0
  As  As9  1  0.250  0.750  0.500  1.0
  O  O10  1  0.537  0.564  0.375  1.0
  O  O11  1  0.436  0.463  0.625  1.0
  O  O12  1  0.939  0.912  0.524  1.0
  O  O13  1  0.088  0.061  0.476  1.0
  O  O14  1  0.880  0.887  0.167  1.0
  O  O15  1  0.113  0.120  0.833  1.0
  O  O16  1  0.049  0.053  0.065  1.0
  O  O17  1  0.947  0.951  0.935  1.0
  O  O18  1  0.488  0.512  0.000  1.0
  O  O19  1  0.836  0.813  0.394  1.0
  O  O20  1  0.187  0.164  0.606  1.0
  O  O21  1  0.207  0.229  0.957  1.0
  O  O22  1  0.771  0.793  0.043  1.0
  O  O23  1  0.726  0.711  0.271  1.0
  O  O24  1  0.289  0.274  0.729  1.0
  O  O25  1  0.983  0.996  0.292  1.0
  O  O26  1  0.004  0.017  0.708  1.0
  O  O27  1  0.651  0.643  0.510  1.0
  O  O28  1  0.357  0.349  0.490  1.0
  O  O29  1  0.154  0.160  0.196  1.0
  O  O30  1  0.840  0.846  0.804  1.0
  O  O31  1  0.253  0.244  0.364  1.0
  O  O32  1  0.756  0.747  0.636  1.0
  O  O33  1  0.609  0.616  0.139  1.0
  O  O34  1  0.384  0.391  0.861  1.0
[/CIF]
.
The crystal structure described by Nb9AsO25 crystallizes in the monoclinic C2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(6), one O(8), and two equivalent O(12) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 4-31°. In the second Nb site, Nb(2) is bonded to one O(11), one O(4), one O(7), one O(9), and two equivalent O(13) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 4-31°. In the third Nb site, Nb(3) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fourth Nb site, Nb(4,5) is bonded to one O(1), one O(13), one O(7), one O(8), and two equivalent O(11) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra;  a cornercorner with one Nb(2)O6 octahedra; corners with two equivalent Nb(4,5)O6 octahedra;  a cornercorner with one As(1)O4 tetrahedra; and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-32°. As(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form AsO4 tetrahedra that share corners with four equivalent Nb(4,5)O6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are thirteen inequivalent O sites. In the first O site, O(8) is bonded in a linear geometry to one Nb(1) and one Nb(4,5) atom. In the second O site, O(9) is bonded in a linear geometry to one Nb(2) and one Nb(4,5) atom. In the third O site, O(10) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(4,5) atoms. In the fourth O site, O(11) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(4,5) atoms. In the fifth O site, O(12) is bonded in a 3-coordinate geometry to one Nb(4,5) and two equivalent Nb(1) atoms. In the sixth O site, O(13) is bonded in a 3-coordinate geometry to one Nb(4,5) and two equivalent Nb(2) atoms. In the seventh O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Nb(4,5) and one As(1) atom. In the eighth O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Nb(4,5) and one As(1) atom. In the ninth O site, O(3) is bonded in a linear geometry to one Nb(1) and one Nb(3) atom. In the tenth O site, O(4) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the eleventh O site, O(5) is bonded in a linear geometry to two equivalent Nb(3) atoms. In the twelfth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(4,5) atom. In the thirteenth O site, O(7) is bonded in a linear geometry to one Nb(2) and one Nb(4,5) atom. is represented by the CIF card [CIF]
data_Nb9AsO25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.383
_cell_length_b   11.383
_cell_length_c   15.865
_cell_angle_alpha   45.825
_cell_angle_beta   45.825
_cell_angle_gamma   19.547
_symmetry_Int_Tables_number   1
_cell_volume   486.355
_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  0.784  0.779  0.326  1.0
  Nb  Nb1  1  0.221  0.216  0.674  1.0
  Nb  Nb2  1  0.107  0.108  0.111  1.0
  Nb  Nb3  1  0.892  0.893  0.889  1.0
  Nb  Nb4  1  0.960  0.040  1.000  1.0
  Nb  Nb5  1  0.681  0.665  0.212  1.0
  Nb  Nb6  1  0.335  0.319  0.788  1.0
  Nb  Nb7  1  0.877  0.892  0.442  1.0
  Nb  Nb8  1  0.108  0.123  0.558  1.0
  As  As9  1  0.250  0.750  0.500  1.0
  O  O10  1  0.537  0.564  0.375  1.0
  O  O11  1  0.436  0.463  0.625  1.0
  O  O12  1  0.939  0.912  0.524  1.0
  O  O13  1  0.088  0.061  0.476  1.0
  O  O14  1  0.880  0.887  0.167  1.0
  O  O15  1  0.113  0.120  0.833  1.0
  O  O16  1  0.049  0.053  0.065  1.0
  O  O17  1  0.947  0.951  0.935  1.0
  O  O18  1  0.488  0.512  0.000  1.0
  O  O19  1  0.836  0.813  0.394  1.0
  O  O20  1  0.187  0.164  0.606  1.0
  O  O21  1  0.207  0.229  0.957  1.0
  O  O22  1  0.771  0.793  0.043  1.0
  O  O23  1  0.726  0.711  0.271  1.0
  O  O24  1  0.289  0.274  0.729  1.0
  O  O25  1  0.983  0.996  0.292  1.0
  O  O26  1  0.004  0.017  0.708  1.0
  O  O27  1  0.651  0.643  0.510  1.0
  O  O28  1  0.357  0.349  0.490  1.0
  O  O29  1  0.154  0.160  0.196  1.0
  O  O30  1  0.840  0.846  0.804  1.0
  O  O31  1  0.253  0.244  0.364  1.0
  O  O32  1  0.756  0.747  0.636  1.0
  O  O33  1  0.609  0.616  0.139  1.0
  O  O34  1  0.384  0.391  0.861  1.0
[/CIF]
.