The material structure described by CuNb3O8 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(4), one O(6), and two equivalent O(7) atoms. In the second Nb site, Nb(2) 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 distorted NbO6 octahedra that share corners with three equivalent Nb(3)O6 octahedra and corners with four equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-59°. In the third Nb site, Nb(3) is bonded to one O(1), one O(2), one O(6), one O(8), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Cu(1)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, and edges with two equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-51°. Cu(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form distorted CuO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and edges with two equivalent Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-59°. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Nb(3) and one Cu(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Cu(1) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(1) atoms. In the fourth O site, O(8) is bonded in a distorted trigonal planar geometry to one Nb(2), one Nb(3), and one Cu(1) atom. In the fifth O site, O(1) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Cu(1) atom. In the seventh O site, O(3) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Cu(1) atom. In the eighth O site, O(4) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Cu(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nb3CuO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.101
_cell_length_b   7.662
_cell_length_c   15.563
_cell_angle_alpha   72.832
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   581.162
_cell_formula_units_Z   4
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  0.740  0.517  0.835  1.0
  Nb  Nb1  1  0.240  0.483  0.665  1.0
  Nb  Nb2  1  0.260  0.483  0.165  1.0
  Nb  Nb3  1  0.760  0.517  0.335  1.0
  Nb  Nb4  1  0.246  0.251  0.924  1.0
  Nb  Nb5  1  0.746  0.749  0.576  1.0
  Nb  Nb6  1  0.754  0.749  0.076  1.0
  Nb  Nb7  1  0.254  0.251  0.424  1.0
  Nb  Nb8  1  0.735  0.008  0.833  1.0
  Nb  Nb9  1  0.235  0.992  0.667  1.0
  Nb  Nb10  1  0.265  0.992  0.167  1.0
  Nb  Nb11  1  0.765  0.008  0.333  1.0
  Cu  Cu12  1  0.742  0.266  0.578  1.0
  Cu  Cu13  1  0.242  0.734  0.922  1.0
  Cu  Cu14  1  0.258  0.734  0.422  1.0
  Cu  Cu15  1  0.758  0.266  0.078  1.0
  O  O16  1  0.920  0.220  0.845  1.0
  O  O17  1  0.420  0.780  0.655  1.0
  O  O18  1  0.080  0.780  0.155  1.0
  O  O19  1  0.580  0.220  0.345  1.0
  O  O20  1  0.425  0.042  0.900  1.0
  O  O21  1  0.925  0.958  0.600  1.0
  O  O22  1  0.575  0.958  0.100  1.0
  O  O23  1  0.075  0.042  0.400  1.0
  O  O24  1  0.572  0.352  0.952  1.0
  O  O25  1  0.072  0.648  0.548  1.0
  O  O26  1  0.428  0.648  0.048  1.0
  O  O27  1  0.928  0.352  0.452  1.0
  O  O28  1  0.067  0.503  0.901  1.0
  O  O29  1  0.567  0.497  0.599  1.0
  O  O30  1  0.933  0.497  0.099  1.0
  O  O31  1  0.433  0.503  0.401  1.0
  O  O32  1  0.931  0.084  0.219  1.0
  O  O33  1  0.431  0.916  0.281  1.0
  O  O34  1  0.069  0.916  0.781  1.0
  O  O35  1  0.569  0.084  0.719  1.0
  O  O36  1  0.902  0.734  0.347  1.0
  O  O37  1  0.402  0.266  0.153  1.0
  O  O38  1  0.098  0.266  0.653  1.0
  O  O39  1  0.598  0.734  0.847  1.0
  O  O40  1  0.085  0.416  0.284  1.0
  O  O41  1  0.585  0.584  0.216  1.0
  O  O42  1  0.915  0.584  0.716  1.0
  O  O43  1  0.415  0.416  0.784  1.0
  O  O44  1  0.600  0.848  0.461  1.0
  O  O45  1  0.100  0.152  0.039  1.0
  O  O46  1  0.400  0.152  0.539  1.0
  O  O47  1  0.900  0.848  0.961  1.0
[/CIF]
.
The material structure described by CuNb3O8 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(4), one O(6), and two equivalent O(7) atoms. In the second Nb site, Nb(2) 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 distorted NbO6 octahedra that share corners with three equivalent Nb(3)O6 octahedra and corners with four equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-59°. In the third Nb site, Nb(3) is bonded to one O(1), one O(2), one O(6), one O(8), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Cu(1)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, and edges with two equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-51°. Cu(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form distorted CuO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and edges with two equivalent Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-59°. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Nb(3) and one Cu(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(3), and one Cu(1) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(1) atoms. In the fourth O site, O(8) is bonded in a distorted trigonal planar geometry to one Nb(2), one Nb(3), and one Cu(1) atom. In the fifth O site, O(1) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Cu(1) atom. In the seventh O site, O(3) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Cu(1) atom. In the eighth O site, O(4) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Cu(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nb3CuO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.101
_cell_length_b   7.662
_cell_length_c   15.563
_cell_angle_alpha   72.832
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   581.162
_cell_formula_units_Z   4
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  0.740  0.517  0.835  1.0
  Nb  Nb1  1  0.240  0.483  0.665  1.0
  Nb  Nb2  1  0.260  0.483  0.165  1.0
  Nb  Nb3  1  0.760  0.517  0.335  1.0
  Nb  Nb4  1  0.246  0.251  0.924  1.0
  Nb  Nb5  1  0.746  0.749  0.576  1.0
  Nb  Nb6  1  0.754  0.749  0.076  1.0
  Nb  Nb7  1  0.254  0.251  0.424  1.0
  Nb  Nb8  1  0.735  0.008  0.833  1.0
  Nb  Nb9  1  0.235  0.992  0.667  1.0
  Nb  Nb10  1  0.265  0.992  0.167  1.0
  Nb  Nb11  1  0.765  0.008  0.333  1.0
  Cu  Cu12  1  0.742  0.266  0.578  1.0
  Cu  Cu13  1  0.242  0.734  0.922  1.0
  Cu  Cu14  1  0.258  0.734  0.422  1.0
  Cu  Cu15  1  0.758  0.266  0.078  1.0
  O  O16  1  0.920  0.220  0.845  1.0
  O  O17  1  0.420  0.780  0.655  1.0
  O  O18  1  0.080  0.780  0.155  1.0
  O  O19  1  0.580  0.220  0.345  1.0
  O  O20  1  0.425  0.042  0.900  1.0
  O  O21  1  0.925  0.958  0.600  1.0
  O  O22  1  0.575  0.958  0.100  1.0
  O  O23  1  0.075  0.042  0.400  1.0
  O  O24  1  0.572  0.352  0.952  1.0
  O  O25  1  0.072  0.648  0.548  1.0
  O  O26  1  0.428  0.648  0.048  1.0
  O  O27  1  0.928  0.352  0.452  1.0
  O  O28  1  0.067  0.503  0.901  1.0
  O  O29  1  0.567  0.497  0.599  1.0
  O  O30  1  0.933  0.497  0.099  1.0
  O  O31  1  0.433  0.503  0.401  1.0
  O  O32  1  0.931  0.084  0.219  1.0
  O  O33  1  0.431  0.916  0.281  1.0
  O  O34  1  0.069  0.916  0.781  1.0
  O  O35  1  0.569  0.084  0.719  1.0
  O  O36  1  0.902  0.734  0.347  1.0
  O  O37  1  0.402  0.266  0.153  1.0
  O  O38  1  0.098  0.266  0.653  1.0
  O  O39  1  0.598  0.734  0.847  1.0
  O  O40  1  0.085  0.416  0.284  1.0
  O  O41  1  0.585  0.584  0.216  1.0
  O  O42  1  0.915  0.584  0.716  1.0
  O  O43  1  0.415  0.416  0.784  1.0
  O  O44  1  0.600  0.848  0.461  1.0
  O  O45  1  0.100  0.152  0.039  1.0
  O  O46  1  0.400  0.152  0.539  1.0
  O  O47  1  0.900  0.848  0.961  1.0
[/CIF]
.