The structure described by Cs3Nb2I9 crystallizes in the trigonal P-3m1 space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to three equivalent I(2), three equivalent I(3), and six equivalent I(1) atoms to form CsI12 cuboctahedra that share corners with three equivalent Cs(2)I12 cuboctahedra, corners with three equivalent Cs(3)I12 cuboctahedra, corners with six equivalent Cs(1)I12 cuboctahedra, faces with three equivalent Cs(2)I12 cuboctahedra, faces with three equivalent Cs(3)I12 cuboctahedra, faces with three equivalent Nb(1)I6 octahedra, and faces with three equivalent Nb(2)I6 octahedra. In the second Cs site, Cs(2) is bonded to three equivalent I(1) and nine equivalent I(2) atoms to form CsI12 cuboctahedra that share corners with three equivalent Cs(1)I12 cuboctahedra, corners with six equivalent Cs(2)I12 cuboctahedra, corners with three equivalent Nb(2)I6 octahedra,  a faceface with one Cs(3)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with three equivalent Cs(2)I12 cuboctahedra, and faces with four equivalent Nb(1)I6 octahedra. The corner-sharing octahedral tilt angles are 28°. In the third Cs site, Cs(3) is bonded to three equivalent I(1) and nine equivalent I(3) atoms to form CsI12 cuboctahedra that share corners with three equivalent Cs(1)I12 cuboctahedra, corners with six equivalent Cs(3)I12 cuboctahedra, corners with three equivalent Nb(1)I6 octahedra,  a faceface with one Cs(2)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with three equivalent Cs(3)I12 cuboctahedra, and faces with four equivalent Nb(2)I6 octahedra. The corner-sharing octahedral tilt angles are 28°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent I(1) and three equivalent I(2) atoms to form distorted NbI6 octahedra that share corners with three equivalent Cs(3)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with four equivalent Cs(2)I12 cuboctahedra, and  a faceface with one Nb(2)I6 octahedra. In the second Nb site, Nb(2) is bonded to three equivalent I(1) and three equivalent I(3) atoms to form distorted NbI6 octahedra that share corners with three equivalent Cs(2)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with four equivalent Cs(3)I12 cuboctahedra, and  a faceface with one Nb(1)I6 octahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 2-coordinate geometry to one Cs(2), one Cs(3), two equivalent Cs(1), one Nb(1), and one Nb(2) atom. In the second I site, I(2) is bonded to one Cs(1), three equivalent Cs(2), and one Nb(1) atom to form a mixture of distorted edge, corner, and face-sharing ICs4Nb square pyramids. In the third I site, I(3) is bonded to one Cs(1), three equivalent Cs(3), and one Nb(2) atom to form a mixture of distorted edge, corner, and face-sharing ICs4Nb square pyramids. is represented by the CIF file [CIF]
data_Cs3Nb2I9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.426
_cell_length_b   8.426
_cell_length_c   19.779
_cell_angle_alpha   89.989
_cell_angle_beta   90.014
_cell_angle_gamma   119.997
_symmetry_Int_Tables_number   1
_cell_volume   1216.092
_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
  Cs  Cs0  1  0.000  0.000  0.250  1.0
  Cs  Cs1  1  1.000  0.000  0.750  1.0
  Cs  Cs2  1  0.333  0.667  0.432  1.0
  Cs  Cs3  1  0.667  0.333  0.568  1.0
  Cs  Cs4  1  0.667  0.333  0.932  1.0
  Cs  Cs5  1  0.333  0.667  0.068  1.0
  Nb  Nb6  1  0.333  0.667  0.679  1.0
  Nb  Nb7  1  0.667  0.333  0.321  1.0
  Nb  Nb8  1  0.667  0.333  0.180  1.0
  Nb  Nb9  1  0.333  0.667  0.820  1.0
  I  I10  1  0.495  0.506  0.250  1.0
  I  I11  1  0.494  0.989  0.250  1.0
  I  I12  1  0.011  0.506  0.250  1.0
  I  I13  1  0.505  0.494  0.750  1.0
  I  I14  1  0.506  0.011  0.750  1.0
  I  I15  1  0.989  0.494  0.750  1.0
  I  I16  1  0.826  0.174  0.406  1.0
  I  I17  1  0.826  0.652  0.406  1.0
  I  I18  1  0.348  0.174  0.406  1.0
  I  I19  1  0.174  0.826  0.594  1.0
  I  I20  1  0.174  0.348  0.594  1.0
  I  I21  1  0.652  0.826  0.594  1.0
  I  I22  1  0.174  0.826  0.906  1.0
  I  I23  1  0.174  0.348  0.906  1.0
  I  I24  1  0.652  0.826  0.906  1.0
  I  I25  1  0.826  0.174  0.095  1.0
  I  I26  1  0.826  0.652  0.094  1.0
  I  I27  1  0.348  0.174  0.094  1.0
[/CIF]
.
The structure described by Cs3Nb2I9 crystallizes in the trigonal P-3m1 space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to three equivalent I(2), three equivalent I(3), and six equivalent I(1) atoms to form CsI12 cuboctahedra that share corners with three equivalent Cs(2)I12 cuboctahedra, corners with three equivalent Cs(3)I12 cuboctahedra, corners with six equivalent Cs(1)I12 cuboctahedra, faces with three equivalent Cs(2)I12 cuboctahedra, faces with three equivalent Cs(3)I12 cuboctahedra, faces with three equivalent Nb(1)I6 octahedra, and faces with three equivalent Nb(2)I6 octahedra. In the second Cs site, Cs(2) is bonded to three equivalent I(1) and nine equivalent I(2) atoms to form CsI12 cuboctahedra that share corners with three equivalent Cs(1)I12 cuboctahedra, corners with six equivalent Cs(2)I12 cuboctahedra, corners with three equivalent Nb(2)I6 octahedra,  a faceface with one Cs(3)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with three equivalent Cs(2)I12 cuboctahedra, and faces with four equivalent Nb(1)I6 octahedra. The corner-sharing octahedral tilt angles are 28°. In the third Cs site, Cs(3) is bonded to three equivalent I(1) and nine equivalent I(3) atoms to form CsI12 cuboctahedra that share corners with three equivalent Cs(1)I12 cuboctahedra, corners with six equivalent Cs(3)I12 cuboctahedra, corners with three equivalent Nb(1)I6 octahedra,  a faceface with one Cs(2)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with three equivalent Cs(3)I12 cuboctahedra, and faces with four equivalent Nb(2)I6 octahedra. The corner-sharing octahedral tilt angles are 28°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent I(1) and three equivalent I(2) atoms to form distorted NbI6 octahedra that share corners with three equivalent Cs(3)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with four equivalent Cs(2)I12 cuboctahedra, and  a faceface with one Nb(2)I6 octahedra. In the second Nb site, Nb(2) is bonded to three equivalent I(1) and three equivalent I(3) atoms to form distorted NbI6 octahedra that share corners with three equivalent Cs(2)I12 cuboctahedra, faces with three equivalent Cs(1)I12 cuboctahedra, faces with four equivalent Cs(3)I12 cuboctahedra, and  a faceface with one Nb(1)I6 octahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 2-coordinate geometry to one Cs(2), one Cs(3), two equivalent Cs(1), one Nb(1), and one Nb(2) atom. In the second I site, I(2) is bonded to one Cs(1), three equivalent Cs(2), and one Nb(1) atom to form a mixture of distorted edge, corner, and face-sharing ICs4Nb square pyramids. In the third I site, I(3) is bonded to one Cs(1), three equivalent Cs(3), and one Nb(2) atom to form a mixture of distorted edge, corner, and face-sharing ICs4Nb square pyramids. is represented by the CIF file [CIF]
data_Cs3Nb2I9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.426
_cell_length_b   8.426
_cell_length_c   19.779
_cell_angle_alpha   89.989
_cell_angle_beta   90.014
_cell_angle_gamma   119.997
_symmetry_Int_Tables_number   1
_cell_volume   1216.092
_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
  Cs  Cs0  1  0.000  0.000  0.250  1.0
  Cs  Cs1  1  1.000  0.000  0.750  1.0
  Cs  Cs2  1  0.333  0.667  0.432  1.0
  Cs  Cs3  1  0.667  0.333  0.568  1.0
  Cs  Cs4  1  0.667  0.333  0.932  1.0
  Cs  Cs5  1  0.333  0.667  0.068  1.0
  Nb  Nb6  1  0.333  0.667  0.679  1.0
  Nb  Nb7  1  0.667  0.333  0.321  1.0
  Nb  Nb8  1  0.667  0.333  0.180  1.0
  Nb  Nb9  1  0.333  0.667  0.820  1.0
  I  I10  1  0.495  0.506  0.250  1.0
  I  I11  1  0.494  0.989  0.250  1.0
  I  I12  1  0.011  0.506  0.250  1.0
  I  I13  1  0.505  0.494  0.750  1.0
  I  I14  1  0.506  0.011  0.750  1.0
  I  I15  1  0.989  0.494  0.750  1.0
  I  I16  1  0.826  0.174  0.406  1.0
  I  I17  1  0.826  0.652  0.406  1.0
  I  I18  1  0.348  0.174  0.406  1.0
  I  I19  1  0.174  0.826  0.594  1.0
  I  I20  1  0.174  0.348  0.594  1.0
  I  I21  1  0.652  0.826  0.594  1.0
  I  I22  1  0.174  0.826  0.906  1.0
  I  I23  1  0.174  0.348  0.906  1.0
  I  I24  1  0.652  0.826  0.906  1.0
  I  I25  1  0.826  0.174  0.095  1.0
  I  I26  1  0.826  0.652  0.094  1.0
  I  I27  1  0.348  0.174  0.094  1.0
[/CIF]
.