The structure described by FeNb2O6 crystallizes in the monoclinic P2/c space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form distorted NbO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra,  an edgeedge with one Fe(2)O6 octahedra, and edges with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-55°. In the second Nb site, Nb(2) is bonded to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted NbO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-55°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(6) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with four equivalent Nb(2)O6 octahedra, edges with two equivalent Nb(2)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-24°. In the second Fe site, Fe(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-26°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Nb(1) and one Fe(2) atom. In the second O site, O(2) is bonded in a T-shaped geometry to one Nb(1) and two equivalent Fe(2) atoms. In the third O site, O(3) is bonded in a T-shaped geometry to one Nb(2) and two equivalent Fe(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Nb(2) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Nb(1) and two equivalent Nb(2) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to two equivalent Nb(2) and one Fe(1) atom. is represented by the CIF file [CIF]
data_Nb2FeO6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.831
_cell_length_b   5.333
_cell_length_c   14.955
_cell_angle_alpha   89.582
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   465.101
_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  0.172  0.484  0.335  1.0
  Nb  Nb1  1  0.669  0.010  0.835  1.0
  Nb  Nb2  1  0.331  0.510  0.835  1.0
  Nb  Nb3  1  0.828  0.984  0.335  1.0
  Nb  Nb4  1  0.828  0.516  0.665  1.0
  Nb  Nb5  1  0.172  0.016  0.665  1.0
  Nb  Nb6  1  0.669  0.490  0.165  1.0
  Nb  Nb7  1  0.331  0.990  0.165  1.0
  Fe  Fe8  1  0.143  0.250  0.000  1.0
  Fe  Fe9  1  0.350  0.750  0.500  1.0
  Fe  Fe10  1  0.857  0.750  0.000  1.0
  Fe  Fe11  1  0.650  0.250  0.500  1.0
  O  O12  1  0.908  0.296  0.398  1.0
  O  O13  1  0.609  0.591  0.582  1.0
  O  O14  1  0.114  0.591  0.918  1.0
  O  O15  1  0.114  0.909  0.082  1.0
  O  O16  1  0.858  0.661  0.259  1.0
  O  O17  1  0.886  0.409  0.082  1.0
  O  O18  1  0.092  0.704  0.602  1.0
  O  O19  1  0.360  0.837  0.759  1.0
  O  O20  1  0.858  0.839  0.741  1.0
  O  O21  1  0.609  0.909  0.418  1.0
  O  O22  1  0.908  0.204  0.602  1.0
  O  O23  1  0.402  0.306  0.102  1.0
  O  O24  1  0.360  0.663  0.241  1.0
  O  O25  1  0.092  0.796  0.398  1.0
  O  O26  1  0.598  0.694  0.898  1.0
  O  O27  1  0.391  0.091  0.582  1.0
  O  O28  1  0.598  0.806  0.102  1.0
  O  O29  1  0.640  0.337  0.759  1.0
  O  O30  1  0.142  0.339  0.741  1.0
  O  O31  1  0.886  0.091  0.918  1.0
  O  O32  1  0.391  0.409  0.418  1.0
  O  O33  1  0.142  0.161  0.259  1.0
  O  O34  1  0.640  0.163  0.241  1.0
  O  O35  1  0.402  0.194  0.898  1.0
[/CIF]
.
The structure described by FeNb2O6 crystallizes in the monoclinic P2/c space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form distorted NbO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra,  an edgeedge with one Fe(2)O6 octahedra, and edges with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-55°. In the second Nb site, Nb(2) is bonded to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted NbO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-55°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(6) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with four equivalent Nb(2)O6 octahedra, edges with two equivalent Nb(2)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-24°. In the second Fe site, Fe(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-26°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Nb(1) and one Fe(2) atom. In the second O site, O(2) is bonded in a T-shaped geometry to one Nb(1) and two equivalent Fe(2) atoms. In the third O site, O(3) is bonded in a T-shaped geometry to one Nb(2) and two equivalent Fe(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Nb(2) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Nb(1) and two equivalent Nb(2) atoms. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to two equivalent Nb(2) and one Fe(1) atom. is represented by the CIF file [CIF]
data_Nb2FeO6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.831
_cell_length_b   5.333
_cell_length_c   14.955
_cell_angle_alpha   89.582
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   465.101
_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  0.172  0.484  0.335  1.0
  Nb  Nb1  1  0.669  0.010  0.835  1.0
  Nb  Nb2  1  0.331  0.510  0.835  1.0
  Nb  Nb3  1  0.828  0.984  0.335  1.0
  Nb  Nb4  1  0.828  0.516  0.665  1.0
  Nb  Nb5  1  0.172  0.016  0.665  1.0
  Nb  Nb6  1  0.669  0.490  0.165  1.0
  Nb  Nb7  1  0.331  0.990  0.165  1.0
  Fe  Fe8  1  0.143  0.250  0.000  1.0
  Fe  Fe9  1  0.350  0.750  0.500  1.0
  Fe  Fe10  1  0.857  0.750  0.000  1.0
  Fe  Fe11  1  0.650  0.250  0.500  1.0
  O  O12  1  0.908  0.296  0.398  1.0
  O  O13  1  0.609  0.591  0.582  1.0
  O  O14  1  0.114  0.591  0.918  1.0
  O  O15  1  0.114  0.909  0.082  1.0
  O  O16  1  0.858  0.661  0.259  1.0
  O  O17  1  0.886  0.409  0.082  1.0
  O  O18  1  0.092  0.704  0.602  1.0
  O  O19  1  0.360  0.837  0.759  1.0
  O  O20  1  0.858  0.839  0.741  1.0
  O  O21  1  0.609  0.909  0.418  1.0
  O  O22  1  0.908  0.204  0.602  1.0
  O  O23  1  0.402  0.306  0.102  1.0
  O  O24  1  0.360  0.663  0.241  1.0
  O  O25  1  0.092  0.796  0.398  1.0
  O  O26  1  0.598  0.694  0.898  1.0
  O  O27  1  0.391  0.091  0.582  1.0
  O  O28  1  0.598  0.806  0.102  1.0
  O  O29  1  0.640  0.337  0.759  1.0
  O  O30  1  0.142  0.339  0.741  1.0
  O  O31  1  0.886  0.091  0.918  1.0
  O  O32  1  0.391  0.409  0.418  1.0
  O  O33  1  0.142  0.161  0.259  1.0
  O  O34  1  0.640  0.163  0.241  1.0
  O  O35  1  0.402  0.194  0.898  1.0
[/CIF]
.