The compound described by K2NaNb3O9 crystallizes in the monoclinic Pm space group. There are four inequivalent K sites. In the first K site, K(1) is bonded to one O(17), one O(18), one O(7), one O(9), two equivalent O(1), two equivalent O(12), two equivalent O(13), and two equivalent O(6) atoms to form KO12 cuboctahedra that share corners with two equivalent K(2)O12 cuboctahedra, corners with two equivalent K(4)O12 cuboctahedra, corners with four equivalent K(3)O12 cuboctahedra,  a faceface with one K(2)O12 cuboctahedra,  a faceface with one K(4)O12 cuboctahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, faces with two equivalent Nb(1)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, and faces with two equivalent Nb(6)O6 octahedra. In the second K site, K(2) is bonded to one O(16), one O(17), one O(8), one O(9), two equivalent O(11), two equivalent O(14), two equivalent O(3), and two equivalent O(6) atoms to form KO12 cuboctahedra that share corners with two equivalent K(1)O12 cuboctahedra, corners with two equivalent K(3)O12 cuboctahedra, corners with two equivalent K(4)O12 cuboctahedra,  a faceface with one K(1)O12 cuboctahedra, faces with two equivalent K(2)O12 cuboctahedra, faces with two equivalent Nb(2)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(5)O6 octahedra, and faces with two equivalent Nb(6)O6 octahedra. In the third K site, K(3) is bonded to one O(17), one O(18), one O(7), one O(9), two equivalent O(1), two equivalent O(12), two equivalent O(15), and two equivalent O(4) atoms to form KO12 cuboctahedra that share corners with two equivalent K(2)O12 cuboctahedra, corners with two equivalent K(4)O12 cuboctahedra, corners with four equivalent K(1)O12 cuboctahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, faces with two equivalent Nb(1)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, and faces with two equivalent Nb(6)O6 octahedra. In the fourth K site, K(4) is bonded to one O(16), one O(18), one O(7), one O(8), two equivalent O(10), two equivalent O(13), two equivalent O(2), and two equivalent O(5) atoms to form KO12 cuboctahedra that share corners with two equivalent K(1)O12 cuboctahedra, corners with two equivalent K(2)O12 cuboctahedra, corners with two equivalent K(3)O12 cuboctahedra,  a faceface with one K(1)O12 cuboctahedra, faces with two equivalent K(4)O12 cuboctahedra, faces with two equivalent Nb(1)O6 octahedra, faces with two equivalent Nb(2)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, and faces with two equivalent Nb(5)O6 octahedra. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 9-coordinate geometry to one O(16), one O(18), one O(8), two equivalent O(10), two equivalent O(14), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 8-coordinate geometry to one O(17), one O(9), two equivalent O(11), two equivalent O(15), and two equivalent O(3) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(12), one O(13), one O(2), one O(4), and two equivalent O(18) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(5)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-18°. In the second Nb site, Nb(2) is bonded to one O(10), one O(14), one O(3), one O(5), and two equivalent O(16) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-18°. In the third Nb site, Nb(3) is bonded to one O(1), one O(11), one O(15), one O(6), and two equivalent O(17) atoms to form 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(3)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-15°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(10), one O(13), one O(4), and two equivalent O(7) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-18°. In the fifth Nb site, Nb(5) is bonded to one O(11), one O(14), one O(2), one O(5), and two equivalent O(8) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-18°. In the sixth Nb site, Nb(6) is bonded to one O(12), one O(15), one O(3), one O(6), and two equivalent O(9) atoms to form 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(3)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-16°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(3), one Nb(3), and one Nb(4) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent K(4), two equivalent Na(1), one Nb(1), and one Nb(5) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent K(2), two equivalent Na(2), one Nb(2), and one Nb(6) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent K(3), one Nb(1), and one Nb(4) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent K(4), one Nb(2), and one Nb(5) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent K(1), two equivalent K(2), one Nb(3), and one Nb(6) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), one K(3), one K(4), and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded to one K(2), one K(4), one Na(1), and two equivalent Nb(5) atoms to form distorted OK2NaNb2 square pyramids that share corners with two equivalent O(13)K4Nb2 octahedra, corners with two equivalent O(8)K2NaNb2 square pyramids, and faces with two equivalent O(14)K2Na2Nb2 octahedra. The corner-sharing octahedral tilt angles are 64°. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to one K(1), one K(2), one K(3), one Na(2), and two equivalent Nb(6) atoms. In the tenth O site, O(10) is bonded in a 6-coordinate geometry to two equivalent K(4), two equivalent Na(1), one Nb(2), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a 6-coordinate geometry to two equivalent K(2), two equivalent Na(2), one Nb(3), and one Nb(5) atom. In the twelfth O site, O(12) is bonded to two equivalent K(1), two equivalent K(3), one Nb(1), and one Nb(6) atom to form distorted OK4Nb2 octahedra that share corners with two equivalent O(15)K2Na2Nb2 octahedra, corners with two equivalent O(13)K4Nb2 octahedra, edges with two equivalent O(12)K4Nb2 octahedra,  a faceface with one O(15)K2Na2Nb2 octahedra, and  a faceface with one O(13)K4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 58-61°. In the thirteenth O site, O(13) is bonded to two equivalent K(1), two equivalent K(4), one Nb(1), and one Nb(4) atom to form distorted OK4Nb2 octahedra that share corners with two equivalent O(12)K4Nb2 octahedra, corners with two equivalent O(8)K2NaNb2 square pyramids, edges with two equivalent O(13)K4Nb2 octahedra, and  a faceface with one O(12)K4Nb2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the fourteenth O site, O(14) is bonded to two equivalent K(2), two equivalent Na(1), one Nb(2), and one Nb(5) atom to form distorted OK2Na2Nb2 octahedra that share edges with two equivalent O(14)K2Na2Nb2 octahedra and faces with two equivalent O(8)K2NaNb2 square pyramids. In the fifteenth O site, O(15) is bonded to two equivalent K(3), two equivalent Na(2), one Nb(3), and one Nb(6) atom to form distorted OK2Na2Nb2 octahedra that share corners with two equivalent O(12)K4Nb2 octahedra, edges with two equivalent O(15)K2Na2Nb2 octahedra, and  a faceface with one O(12)K4Nb2 octahedra. The corner-sharing octahedral tilt angles are 61°. In the sixteenth O site, O(16) is bonded in a 2-coordinate geometry to one K(2), one K(4), one Na(1), and two equivalent Nb(2) atoms. In the seventeenth O site, O(17) is bonded in a 2-coordinate geometry to one K(1), one K(2), one K(3), one Na(2), and two equivalent Nb(3) atoms. In the eighteenth O site, O(18) is bonded in a 2-coordinate geometry to one K(1), one K(3), one K(4), one Na(1), and two equivalent Nb(1) atoms. is represented by the CIF file [CIF]
data_K2NaNb3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.009
_cell_length_b   8.114
_cell_length_c   13.043
_cell_angle_alpha   72.331
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   404.231
_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
  K  K0  1  0.000  0.487  0.509  1.0
  K  K1  1  0.000  0.653  0.169  1.0
  K  K2  1  0.000  0.986  0.502  1.0
  K  K3  1  0.000  0.319  0.836  1.0
  Na  Na4  1  0.000  0.807  0.854  1.0
  Na  Na5  1  0.000  0.140  0.187  1.0
  Nb  Nb6  1  0.500  0.648  0.680  1.0
  Nb  Nb7  1  0.500  0.981  0.012  1.0
  Nb  Nb8  1  0.500  0.313  0.344  1.0
  Nb  Nb9  1  0.500  0.140  0.678  1.0
  Nb  Nb10  1  0.500  0.476  0.010  1.0
  Nb  Nb11  1  0.500  0.813  0.342  1.0
  O  O12  1  0.500  0.261  0.495  1.0
  O  O13  1  0.500  0.607  0.830  1.0
  O  O14  1  0.500  0.940  0.162  1.0
  O  O15  1  0.500  0.922  0.653  1.0
  O  O16  1  0.500  0.257  0.985  1.0
  O  O17  1  0.500  0.589  0.321  1.0
  O  O18  1  0.000  0.166  0.664  1.0
  O  O19  1  0.000  0.506  0.994  1.0
  O  O20  1  0.000  0.840  0.326  1.0
  O  O21  1  0.500  0.061  0.829  1.0
  O  O22  1  0.500  0.396  0.161  1.0
  O  O23  1  0.500  0.739  0.494  1.0
  O  O24  1  0.500  0.414  0.675  1.0
  O  O25  1  0.500  0.747  0.007  1.0
  O  O26  1  0.500  0.081  0.337  1.0
  O  O27  1  0.000  0.001  0.996  1.0
  O  O28  1  0.000  0.334  0.327  1.0
  O  O29  1  0.000  0.670  0.665  1.0
[/CIF]
.
The compound described by K2NaNb3O9 crystallizes in the monoclinic Pm space group. There are four inequivalent K sites. In the first K site, K(1) is bonded to one O(17), one O(18), one O(7), one O(9), two equivalent O(1), two equivalent O(12), two equivalent O(13), and two equivalent O(6) atoms to form KO12 cuboctahedra that share corners with two equivalent K(2)O12 cuboctahedra, corners with two equivalent K(4)O12 cuboctahedra, corners with four equivalent K(3)O12 cuboctahedra,  a faceface with one K(2)O12 cuboctahedra,  a faceface with one K(4)O12 cuboctahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, faces with two equivalent Nb(1)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, and faces with two equivalent Nb(6)O6 octahedra. In the second K site, K(2) is bonded to one O(16), one O(17), one O(8), one O(9), two equivalent O(11), two equivalent O(14), two equivalent O(3), and two equivalent O(6) atoms to form KO12 cuboctahedra that share corners with two equivalent K(1)O12 cuboctahedra, corners with two equivalent K(3)O12 cuboctahedra, corners with two equivalent K(4)O12 cuboctahedra,  a faceface with one K(1)O12 cuboctahedra, faces with two equivalent K(2)O12 cuboctahedra, faces with two equivalent Nb(2)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(5)O6 octahedra, and faces with two equivalent Nb(6)O6 octahedra. In the third K site, K(3) is bonded to one O(17), one O(18), one O(7), one O(9), two equivalent O(1), two equivalent O(12), two equivalent O(15), and two equivalent O(4) atoms to form KO12 cuboctahedra that share corners with two equivalent K(2)O12 cuboctahedra, corners with two equivalent K(4)O12 cuboctahedra, corners with four equivalent K(1)O12 cuboctahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, faces with two equivalent Nb(1)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, and faces with two equivalent Nb(6)O6 octahedra. In the fourth K site, K(4) is bonded to one O(16), one O(18), one O(7), one O(8), two equivalent O(10), two equivalent O(13), two equivalent O(2), and two equivalent O(5) atoms to form KO12 cuboctahedra that share corners with two equivalent K(1)O12 cuboctahedra, corners with two equivalent K(2)O12 cuboctahedra, corners with two equivalent K(3)O12 cuboctahedra,  a faceface with one K(1)O12 cuboctahedra, faces with two equivalent K(4)O12 cuboctahedra, faces with two equivalent Nb(1)O6 octahedra, faces with two equivalent Nb(2)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, and faces with two equivalent Nb(5)O6 octahedra. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 9-coordinate geometry to one O(16), one O(18), one O(8), two equivalent O(10), two equivalent O(14), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 8-coordinate geometry to one O(17), one O(9), two equivalent O(11), two equivalent O(15), and two equivalent O(3) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(12), one O(13), one O(2), one O(4), and two equivalent O(18) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(5)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-18°. In the second Nb site, Nb(2) is bonded to one O(10), one O(14), one O(3), one O(5), and two equivalent O(16) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-18°. In the third Nb site, Nb(3) is bonded to one O(1), one O(11), one O(15), one O(6), and two equivalent O(17) atoms to form 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(3)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-15°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(10), one O(13), one O(4), and two equivalent O(7) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(3)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-18°. In the fifth Nb site, Nb(5) is bonded to one O(11), one O(14), one O(2), one O(5), and two equivalent O(8) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(4)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-18°. In the sixth Nb site, Nb(6) is bonded to one O(12), one O(15), one O(3), one O(6), and two equivalent O(9) atoms to form 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(3)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra, faces with two equivalent K(1)O12 cuboctahedra, faces with two equivalent K(2)O12 cuboctahedra, and faces with two equivalent K(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-16°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(3), one Nb(3), and one Nb(4) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent K(4), two equivalent Na(1), one Nb(1), and one Nb(5) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent K(2), two equivalent Na(2), one Nb(2), and one Nb(6) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent K(3), one Nb(1), and one Nb(4) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent K(4), one Nb(2), and one Nb(5) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent K(1), two equivalent K(2), one Nb(3), and one Nb(6) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), one K(3), one K(4), and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded to one K(2), one K(4), one Na(1), and two equivalent Nb(5) atoms to form distorted OK2NaNb2 square pyramids that share corners with two equivalent O(13)K4Nb2 octahedra, corners with two equivalent O(8)K2NaNb2 square pyramids, and faces with two equivalent O(14)K2Na2Nb2 octahedra. The corner-sharing octahedral tilt angles are 64°. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to one K(1), one K(2), one K(3), one Na(2), and two equivalent Nb(6) atoms. In the tenth O site, O(10) is bonded in a 6-coordinate geometry to two equivalent K(4), two equivalent Na(1), one Nb(2), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a 6-coordinate geometry to two equivalent K(2), two equivalent Na(2), one Nb(3), and one Nb(5) atom. In the twelfth O site, O(12) is bonded to two equivalent K(1), two equivalent K(3), one Nb(1), and one Nb(6) atom to form distorted OK4Nb2 octahedra that share corners with two equivalent O(15)K2Na2Nb2 octahedra, corners with two equivalent O(13)K4Nb2 octahedra, edges with two equivalent O(12)K4Nb2 octahedra,  a faceface with one O(15)K2Na2Nb2 octahedra, and  a faceface with one O(13)K4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 58-61°. In the thirteenth O site, O(13) is bonded to two equivalent K(1), two equivalent K(4), one Nb(1), and one Nb(4) atom to form distorted OK4Nb2 octahedra that share corners with two equivalent O(12)K4Nb2 octahedra, corners with two equivalent O(8)K2NaNb2 square pyramids, edges with two equivalent O(13)K4Nb2 octahedra, and  a faceface with one O(12)K4Nb2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the fourteenth O site, O(14) is bonded to two equivalent K(2), two equivalent Na(1), one Nb(2), and one Nb(5) atom to form distorted OK2Na2Nb2 octahedra that share edges with two equivalent O(14)K2Na2Nb2 octahedra and faces with two equivalent O(8)K2NaNb2 square pyramids. In the fifteenth O site, O(15) is bonded to two equivalent K(3), two equivalent Na(2), one Nb(3), and one Nb(6) atom to form distorted OK2Na2Nb2 octahedra that share corners with two equivalent O(12)K4Nb2 octahedra, edges with two equivalent O(15)K2Na2Nb2 octahedra, and  a faceface with one O(12)K4Nb2 octahedra. The corner-sharing octahedral tilt angles are 61°. In the sixteenth O site, O(16) is bonded in a 2-coordinate geometry to one K(2), one K(4), one Na(1), and two equivalent Nb(2) atoms. In the seventeenth O site, O(17) is bonded in a 2-coordinate geometry to one K(1), one K(2), one K(3), one Na(2), and two equivalent Nb(3) atoms. In the eighteenth O site, O(18) is bonded in a 2-coordinate geometry to one K(1), one K(3), one K(4), one Na(1), and two equivalent Nb(1) atoms. is represented by the CIF file [CIF]
data_K2NaNb3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.009
_cell_length_b   8.114
_cell_length_c   13.043
_cell_angle_alpha   72.331
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   404.231
_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
  K  K0  1  0.000  0.487  0.509  1.0
  K  K1  1  0.000  0.653  0.169  1.0
  K  K2  1  0.000  0.986  0.502  1.0
  K  K3  1  0.000  0.319  0.836  1.0
  Na  Na4  1  0.000  0.807  0.854  1.0
  Na  Na5  1  0.000  0.140  0.187  1.0
  Nb  Nb6  1  0.500  0.648  0.680  1.0
  Nb  Nb7  1  0.500  0.981  0.012  1.0
  Nb  Nb8  1  0.500  0.313  0.344  1.0
  Nb  Nb9  1  0.500  0.140  0.678  1.0
  Nb  Nb10  1  0.500  0.476  0.010  1.0
  Nb  Nb11  1  0.500  0.813  0.342  1.0
  O  O12  1  0.500  0.261  0.495  1.0
  O  O13  1  0.500  0.607  0.830  1.0
  O  O14  1  0.500  0.940  0.162  1.0
  O  O15  1  0.500  0.922  0.653  1.0
  O  O16  1  0.500  0.257  0.985  1.0
  O  O17  1  0.500  0.589  0.321  1.0
  O  O18  1  0.000  0.166  0.664  1.0
  O  O19  1  0.000  0.506  0.994  1.0
  O  O20  1  0.000  0.840  0.326  1.0
  O  O21  1  0.500  0.061  0.829  1.0
  O  O22  1  0.500  0.396  0.161  1.0
  O  O23  1  0.500  0.739  0.494  1.0
  O  O24  1  0.500  0.414  0.675  1.0
  O  O25  1  0.500  0.747  0.007  1.0
  O  O26  1  0.500  0.081  0.337  1.0
  O  O27  1  0.000  0.001  0.996  1.0
  O  O28  1  0.000  0.334  0.327  1.0
  O  O29  1  0.000  0.670  0.665  1.0
[/CIF]
.