The crystal structure described by Na2Nb4O11 crystallizes in the monoclinic Cc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(9) atom. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(10), one O(11), one O(3), one O(7), one O(8), and one O(9) atom to form distorted NbO7 pentagonal bipyramids that share corners with two equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(3)O7 pentagonal bipyramid, and edges with two equivalent Nb(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 43-48°. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(2), one O(4), one O(8), and one O(9) atom. In the third Nb site, Nb(3) is bonded to one O(10), one O(11), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted NbO7 pentagonal bipyramids that share corners with two equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(1)O7 pentagonal bipyramid, and edges with two equivalent Nb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 46-48°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form corner-sharing NbO6 octahedra. There are eleven inequivalent O sites. In the first O site, O(5) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(3), and one Nb(4) atom. In the second O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(3), and one Nb(4) atom. In the third O site, O(7) is bonded in a 2-coordinate geometry to one Nb(1) and one Nb(3) atom. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the fifth O site, O(9) is bonded to one Na(1), one Nb(1), one Nb(2), and one Nb(3) atom to form distorted edge-sharing ONaNb3 tetrahedra. In the sixth O site, O(10) is bonded in a 4-coordinate geometry to one Na(2), one Nb(1), one Nb(2), and one Nb(3) atom. In the seventh O site, O(11) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the eighth O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(1), and one Nb(4) atom. In the ninth O site, O(2) is bonded to one Na(1), one Na(2), one Nb(2), and one Nb(4) atom to form distorted edge-sharing ONa2Nb2 trigonal pyramids. In the tenth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(1), and one Nb(4) atom. In the eleventh O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(2), and one Nb(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Nb4O11
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.334
_cell_length_b   6.334
_cell_length_c   12.960
_cell_angle_alpha   76.064
_cell_angle_beta   76.064
_cell_angle_gamma   59.139
_symmetry_Int_Tables_number   1
_cell_volume   428.865
_cell_formula_units_Z   2
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
  Na  Na0  1  0.334  0.848  0.497  1.0
  Na  Na1  1  0.848  0.334  0.997  1.0
  Na  Na2  1  0.177  0.668  0.996  1.0
  Na  Na3  1  0.668  0.177  0.496  1.0
  Nb  Nb4  1  0.753  0.609  0.253  1.0
  Nb  Nb5  1  0.609  0.753  0.753  1.0
  Nb  Nb6  1  0.392  0.248  0.253  1.0
  Nb  Nb7  1  0.248  0.392  0.753  1.0
  Nb  Nb8  1  0.125  0.885  0.241  1.0
  Nb  Nb9  1  0.885  0.125  0.741  1.0
  Nb  Nb10  1  0.525  0.000  0.998  1.0
  Nb  Nb11  1  0.000  0.525  0.498  1.0
  O  O12  1  0.747  0.719  0.094  1.0
  O  O13  1  0.719  0.747  0.594  1.0
  O  O14  1  0.277  0.257  0.408  1.0
  O  O15  1  0.257  0.277  0.908  1.0
  O  O16  1  0.751  0.565  0.409  1.0
  O  O17  1  0.565  0.751  0.909  1.0
  O  O18  1  0.437  0.243  0.094  1.0
  O  O19  1  0.243  0.437  0.594  1.0
  O  O20  1  0.221  0.939  0.092  1.0
  O  O21  1  0.939  0.221  0.592  1.0
  O  O22  1  0.054  0.785  0.410  1.0
  O  O23  1  0.785  0.054  0.910  1.0
  O  O24  1  0.989  0.251  0.251  1.0
  O  O25  1  0.251  0.989  0.751  1.0
  O  O26  1  0.751  0.003  0.251  1.0
  O  O27  1  0.003  0.751  0.751  1.0
  O  O28  1  0.403  0.907  0.284  1.0
  O  O29  1  0.907  0.403  0.784  1.0
  O  O30  1  0.095  0.592  0.218  1.0
  O  O31  1  0.592  0.095  0.718  1.0
  O  O32  1  0.494  0.507  0.251  1.0
  O  O33  1  0.507  0.494  0.751  1.0
[/CIF]
.
The crystal structure described by Na2Nb4O11 crystallizes in the monoclinic Cc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(9) atom. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(10), one O(11), one O(3), one O(7), one O(8), and one O(9) atom to form distorted NbO7 pentagonal bipyramids that share corners with two equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(3)O7 pentagonal bipyramid, and edges with two equivalent Nb(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 43-48°. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(2), one O(4), one O(8), and one O(9) atom. In the third Nb site, Nb(3) is bonded to one O(10), one O(11), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted NbO7 pentagonal bipyramids that share corners with two equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(1)O7 pentagonal bipyramid, and edges with two equivalent Nb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 46-48°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form corner-sharing NbO6 octahedra. There are eleven inequivalent O sites. In the first O site, O(5) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(3), and one Nb(4) atom. In the second O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(3), and one Nb(4) atom. In the third O site, O(7) is bonded in a 2-coordinate geometry to one Nb(1) and one Nb(3) atom. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the fifth O site, O(9) is bonded to one Na(1), one Nb(1), one Nb(2), and one Nb(3) atom to form distorted edge-sharing ONaNb3 tetrahedra. In the sixth O site, O(10) is bonded in a 4-coordinate geometry to one Na(2), one Nb(1), one Nb(2), and one Nb(3) atom. In the seventh O site, O(11) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the eighth O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(1), and one Nb(4) atom. In the ninth O site, O(2) is bonded to one Na(1), one Na(2), one Nb(2), and one Nb(4) atom to form distorted edge-sharing ONa2Nb2 trigonal pyramids. In the tenth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(1), and one Nb(4) atom. In the eleventh O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Nb(2), and one Nb(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Nb4O11
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.334
_cell_length_b   6.334
_cell_length_c   12.960
_cell_angle_alpha   76.064
_cell_angle_beta   76.064
_cell_angle_gamma   59.139
_symmetry_Int_Tables_number   1
_cell_volume   428.865
_cell_formula_units_Z   2
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
  Na  Na0  1  0.334  0.848  0.497  1.0
  Na  Na1  1  0.848  0.334  0.997  1.0
  Na  Na2  1  0.177  0.668  0.996  1.0
  Na  Na3  1  0.668  0.177  0.496  1.0
  Nb  Nb4  1  0.753  0.609  0.253  1.0
  Nb  Nb5  1  0.609  0.753  0.753  1.0
  Nb  Nb6  1  0.392  0.248  0.253  1.0
  Nb  Nb7  1  0.248  0.392  0.753  1.0
  Nb  Nb8  1  0.125  0.885  0.241  1.0
  Nb  Nb9  1  0.885  0.125  0.741  1.0
  Nb  Nb10  1  0.525  0.000  0.998  1.0
  Nb  Nb11  1  0.000  0.525  0.498  1.0
  O  O12  1  0.747  0.719  0.094  1.0
  O  O13  1  0.719  0.747  0.594  1.0
  O  O14  1  0.277  0.257  0.408  1.0
  O  O15  1  0.257  0.277  0.908  1.0
  O  O16  1  0.751  0.565  0.409  1.0
  O  O17  1  0.565  0.751  0.909  1.0
  O  O18  1  0.437  0.243  0.094  1.0
  O  O19  1  0.243  0.437  0.594  1.0
  O  O20  1  0.221  0.939  0.092  1.0
  O  O21  1  0.939  0.221  0.592  1.0
  O  O22  1  0.054  0.785  0.410  1.0
  O  O23  1  0.785  0.054  0.910  1.0
  O  O24  1  0.989  0.251  0.251  1.0
  O  O25  1  0.251  0.989  0.751  1.0
  O  O26  1  0.751  0.003  0.251  1.0
  O  O27  1  0.003  0.751  0.751  1.0
  O  O28  1  0.403  0.907  0.284  1.0
  O  O29  1  0.907  0.403  0.784  1.0
  O  O30  1  0.095  0.592  0.218  1.0
  O  O31  1  0.592  0.095  0.718  1.0
  O  O32  1  0.494  0.507  0.251  1.0
  O  O33  1  0.507  0.494  0.751  1.0
[/CIF]
.