The crystal structure described by Ba3Nb16O23 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(5), and four equivalent O(4) atoms to form BaO12 cuboctahedra that share corners with two equivalent Ba(2)O12 cuboctahedra, corners with four equivalent Nb(1)O5 square pyramids,  a faceface with one Ba(2)O12 cuboctahedra, faces with two equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Nb(1)O5 square pyramids, and faces with four equivalent Nb(2)O5 square pyramids. In the second Ba site, Ba(2) is bonded to four equivalent O(1), four equivalent O(5), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(2)O12 cuboctahedra, and faces with eight equivalent Nb(2)O5 square pyramids. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), two equivalent O(3), and two equivalent O(4) atoms to form NbO5 square pyramids that share corners with two equivalent Ba(1)O12 cuboctahedra, corners with two equivalent Nb(2)O5 square pyramids, corners with three equivalent Nb(1)O5 square pyramids,  an edgeedge with one Nb(1)O5 square pyramid, and faces with two equivalent Ba(1)O12 cuboctahedra. In the second Nb site, Nb(2) is bonded to one O(1), one O(4), one O(6), and two equivalent O(5) atoms to form NbO5 square pyramids that share corners with two equivalent Nb(1)O5 square pyramids, corners with four equivalent Nb(2)O5 square pyramids, faces with two equivalent Ba(1)O12 cuboctahedra, and faces with two equivalent Ba(2)O12 cuboctahedra. In the third Nb site, Nb(3) is bonded in a square co-planar geometry to one O(2), one O(8), and two equivalent O(7) atoms. In the fourth Nb site, Nb(4) is bonded in a rectangular see-saw-like geometry to one O(3), one O(5), one O(7), and one O(9) atom. In the fifth Nb site, Nb(5) is bonded in a square co-planar geometry to one O(6), one O(8), and two equivalent O(9) atoms. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Ba(1), one Nb(3), and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ba(1), one Nb(4), and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Ba(1), one Nb(2), and two equivalent Nb(1) atoms to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ba(1), one Ba(2), one Nb(4), and two equivalent Nb(2) atoms. In the sixth O site, O(6) is bonded to two equivalent Ba(2), one Nb(5), and two equivalent Nb(2) atoms to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to two equivalent Nb(3) and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a square co-planar geometry to two equivalent Nb(3) and two equivalent Nb(5) atoms. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to two equivalent Nb(4) and two equivalent Nb(5) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba3Nb16O23
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.295
_cell_length_b   12.295
_cell_length_c   4.201
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   118.486
_symmetry_Int_Tables_number   1
_cell_volume   558.172
_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
  Ba  Ba0  1  0.201  0.799  0.000  1.0
  Ba  Ba1  1  0.799  0.201  0.000  1.0
  Ba  Ba2  1  0.000  0.000  0.000  1.0
  Nb  Nb3  1  0.472  0.862  0.500  1.0
  Nb  Nb4  1  0.528  0.138  0.500  1.0
  Nb  Nb5  1  0.862  0.472  0.500  1.0
  Nb  Nb6  1  0.138  0.528  0.500  1.0
  Nb  Nb7  1  0.730  0.932  0.500  1.0
  Nb  Nb8  1  0.270  0.068  0.500  1.0
  Nb  Nb9  1  0.932  0.730  0.500  1.0
  Nb  Nb10  1  0.068  0.270  0.500  1.0
  Nb  Nb11  1  0.601  0.399  0.500  1.0
  Nb  Nb12  1  0.399  0.601  0.500  1.0
  Nb  Nb13  1  0.569  0.773  0.000  1.0
  Nb  Nb14  1  0.431  0.227  0.000  1.0
  Nb  Nb15  1  0.773  0.569  0.000  1.0
  Nb  Nb16  1  0.227  0.431  0.000  1.0
  Nb  Nb17  1  0.673  0.673  0.500  1.0
  Nb  Nb18  1  0.327  0.327  0.500  1.0
  O  O19  1  0.103  0.897  0.500  1.0
  O  O20  1  0.897  0.103  0.500  1.0
  O  O21  1  0.701  0.299  0.500  1.0
  O  O22  1  0.299  0.701  0.500  1.0
  O  O23  1  0.540  0.140  0.000  1.0
  O  O24  1  0.460  0.860  0.000  1.0
  O  O25  1  0.140  0.540  0.000  1.0
  O  O26  1  0.860  0.460  0.000  1.0
  O  O27  1  0.634  0.034  0.500  1.0
  O  O28  1  0.366  0.966  0.500  1.0
  O  O29  1  0.034  0.634  0.500  1.0
  O  O30  1  0.966  0.366  0.500  1.0
  O  O31  1  0.740  0.938  0.000  1.0
  O  O32  1  0.260  0.062  0.000  1.0
  O  O33  1  0.938  0.740  0.000  1.0
  O  O34  1  0.062  0.260  0.000  1.0
  O  O35  1  0.841  0.841  0.500  1.0
  O  O36  1  0.159  0.159  0.500  1.0
  O  O37  1  0.597  0.403  0.000  1.0
  O  O38  1  0.500  0.500  0.500  1.0
  O  O39  1  0.334  0.334  0.000  1.0
  O  O40  1  0.666  0.666  0.000  1.0
  O  O41  1  0.403  0.597  0.000  1.0
[/CIF]
.
The crystal structure described by Ba3Nb16O23 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(5), and four equivalent O(4) atoms to form BaO12 cuboctahedra that share corners with two equivalent Ba(2)O12 cuboctahedra, corners with four equivalent Nb(1)O5 square pyramids,  a faceface with one Ba(2)O12 cuboctahedra, faces with two equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Nb(1)O5 square pyramids, and faces with four equivalent Nb(2)O5 square pyramids. In the second Ba site, Ba(2) is bonded to four equivalent O(1), four equivalent O(5), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(2)O12 cuboctahedra, and faces with eight equivalent Nb(2)O5 square pyramids. There are five inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), two equivalent O(3), and two equivalent O(4) atoms to form NbO5 square pyramids that share corners with two equivalent Ba(1)O12 cuboctahedra, corners with two equivalent Nb(2)O5 square pyramids, corners with three equivalent Nb(1)O5 square pyramids,  an edgeedge with one Nb(1)O5 square pyramid, and faces with two equivalent Ba(1)O12 cuboctahedra. In the second Nb site, Nb(2) is bonded to one O(1), one O(4), one O(6), and two equivalent O(5) atoms to form NbO5 square pyramids that share corners with two equivalent Nb(1)O5 square pyramids, corners with four equivalent Nb(2)O5 square pyramids, faces with two equivalent Ba(1)O12 cuboctahedra, and faces with two equivalent Ba(2)O12 cuboctahedra. In the third Nb site, Nb(3) is bonded in a square co-planar geometry to one O(2), one O(8), and two equivalent O(7) atoms. In the fourth Nb site, Nb(4) is bonded in a rectangular see-saw-like geometry to one O(3), one O(5), one O(7), and one O(9) atom. In the fifth Nb site, Nb(5) is bonded in a square co-planar geometry to one O(6), one O(8), and two equivalent O(9) atoms. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Ba(1), one Nb(3), and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ba(1), one Nb(4), and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Ba(1), one Nb(2), and two equivalent Nb(1) atoms to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ba(1), one Ba(2), one Nb(4), and two equivalent Nb(2) atoms. In the sixth O site, O(6) is bonded to two equivalent Ba(2), one Nb(5), and two equivalent Nb(2) atoms to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to two equivalent Nb(3) and two equivalent Nb(4) atoms. In the eighth O site, O(8) is bonded in a square co-planar geometry to two equivalent Nb(3) and two equivalent Nb(5) atoms. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to two equivalent Nb(4) and two equivalent Nb(5) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba3Nb16O23
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.295
_cell_length_b   12.295
_cell_length_c   4.201
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   118.486
_symmetry_Int_Tables_number   1
_cell_volume   558.172
_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
  Ba  Ba0  1  0.201  0.799  0.000  1.0
  Ba  Ba1  1  0.799  0.201  0.000  1.0
  Ba  Ba2  1  0.000  0.000  0.000  1.0
  Nb  Nb3  1  0.472  0.862  0.500  1.0
  Nb  Nb4  1  0.528  0.138  0.500  1.0
  Nb  Nb5  1  0.862  0.472  0.500  1.0
  Nb  Nb6  1  0.138  0.528  0.500  1.0
  Nb  Nb7  1  0.730  0.932  0.500  1.0
  Nb  Nb8  1  0.270  0.068  0.500  1.0
  Nb  Nb9  1  0.932  0.730  0.500  1.0
  Nb  Nb10  1  0.068  0.270  0.500  1.0
  Nb  Nb11  1  0.601  0.399  0.500  1.0
  Nb  Nb12  1  0.399  0.601  0.500  1.0
  Nb  Nb13  1  0.569  0.773  0.000  1.0
  Nb  Nb14  1  0.431  0.227  0.000  1.0
  Nb  Nb15  1  0.773  0.569  0.000  1.0
  Nb  Nb16  1  0.227  0.431  0.000  1.0
  Nb  Nb17  1  0.673  0.673  0.500  1.0
  Nb  Nb18  1  0.327  0.327  0.500  1.0
  O  O19  1  0.103  0.897  0.500  1.0
  O  O20  1  0.897  0.103  0.500  1.0
  O  O21  1  0.701  0.299  0.500  1.0
  O  O22  1  0.299  0.701  0.500  1.0
  O  O23  1  0.540  0.140  0.000  1.0
  O  O24  1  0.460  0.860  0.000  1.0
  O  O25  1  0.140  0.540  0.000  1.0
  O  O26  1  0.860  0.460  0.000  1.0
  O  O27  1  0.634  0.034  0.500  1.0
  O  O28  1  0.366  0.966  0.500  1.0
  O  O29  1  0.034  0.634  0.500  1.0
  O  O30  1  0.966  0.366  0.500  1.0
  O  O31  1  0.740  0.938  0.000  1.0
  O  O32  1  0.260  0.062  0.000  1.0
  O  O33  1  0.938  0.740  0.000  1.0
  O  O34  1  0.062  0.260  0.000  1.0
  O  O35  1  0.841  0.841  0.500  1.0
  O  O36  1  0.159  0.159  0.500  1.0
  O  O37  1  0.597  0.403  0.000  1.0
  O  O38  1  0.500  0.500  0.500  1.0
  O  O39  1  0.334  0.334  0.000  1.0
  O  O40  1  0.666  0.666  0.000  1.0
  O  O41  1  0.403  0.597  0.000  1.0
[/CIF]
.