The material structure described by Cs2Ti4O9 crystallizes in the monoclinic C2/m space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(6), and four equivalent O(5) atoms. In the second Cs site, Cs(2) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(9) atoms. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(6), one O(8), and two equivalent O(1) atoms. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), one O(4), and three equivalent O(7) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 29°. In the third Ti site, Ti(3) is bonded to one O(1), one O(3), one O(7), one O(9), and two equivalent O(4) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 30°. In the fourth Ti site, Ti(4) is bonded to one O(1), one O(5), one O(6), one O(9), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 31°. There are nine inequivalent O sites. In the first O site, O(5) is bonded in a single-bond geometry to two equivalent Cs(2), four equivalent Cs(1), and one Ti(4) atom. In the second O site, O(6) is bonded in a distorted linear geometry to two equivalent Cs(1), one Ti(1), and one Ti(4) atom. In the third O site, O(7) is bonded to one Ti(3) and three equivalent Ti(2) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to one Ti(1) and two equivalent Ti(4) atoms. In the fifth O site, O(9) is bonded in a 4-coordinate geometry to two equivalent Cs(2), one Ti(3), and one Ti(4) atom. In the sixth O site, O(1) is bonded to one Ti(3), one Ti(4), and two equivalent Ti(1) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the seventh O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Cs(1), one Ti(1), and one Ti(2) atom. In the eighth O site, O(3) is bonded in a distorted water-like geometry to two equivalent Cs(2), one Ti(2), and one Ti(3) atom. In the ninth O site, O(4) is bonded to one Ti(1), one Ti(2), and two equivalent Ti(3) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. is represented by the CIF file [CIF]
data_Cs2Ti4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.828
_cell_length_b   10.352
_cell_length_c   12.101
_cell_angle_alpha   106.800
_cell_angle_beta   90.000
_cell_angle_gamma   100.653
_symmetry_Int_Tables_number   1
_cell_volume   450.396
_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  0.586  0.172  0.583  1.0
  Cs  Cs1  1  0.414  0.828  0.417  1.0
  Cs  Cs2  1  0.515  0.031  0.839  1.0
  Cs  Cs3  1  0.485  0.969  0.161  1.0
  Ti  Ti4  1  0.753  0.506  0.334  1.0
  Ti  Ti5  1  0.247  0.494  0.666  1.0
  Ti  Ti6  1  0.208  0.416  0.897  1.0
  Ti  Ti7  1  0.792  0.584  0.103  1.0
  Ti  Ti8  1  0.829  0.658  0.876  1.0
  Ti  Ti9  1  0.171  0.342  0.124  1.0
  Ti  Ti10  1  0.866  0.731  0.642  1.0
  Ti  Ti11  1  0.134  0.269  0.358  1.0
  O  O12  1  0.766  0.533  0.700  1.0
  O  O13  1  0.234  0.467  0.300  1.0
  O  O14  1  0.828  0.656  0.257  1.0
  O  O15  1  0.172  0.344  0.743  1.0
  O  O16  1  0.134  0.269  0.961  1.0
  O  O17  1  0.866  0.731  0.039  1.0
  O  O18  1  0.303  0.606  0.860  1.0
  O  O19  1  0.697  0.394  0.140  1.0
  O  O20  1  0.948  0.895  0.627  1.0
  O  O21  1  0.052  0.105  0.373  1.0
  O  O22  1  0.811  0.621  0.475  1.0
  O  O23  1  0.189  0.379  0.525  1.0
  O  O24  1  0.732  0.464  0.922  1.0
  O  O25  1  0.268  0.536  0.078  1.0
  O  O26  1  0.659  0.319  0.355  1.0
  O  O27  1  0.341  0.681  0.645  1.0
  O  O28  1  0.901  0.801  0.820  1.0
  O  O29  1  0.099  0.199  0.180  1.0
[/CIF]
.
The material structure described by Cs2Ti4O9 crystallizes in the monoclinic C2/m space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(6), and four equivalent O(5) atoms. In the second Cs site, Cs(2) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(9) atoms. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(6), one O(8), and two equivalent O(1) atoms. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), one O(4), and three equivalent O(7) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 29°. In the third Ti site, Ti(3) is bonded to one O(1), one O(3), one O(7), one O(9), and two equivalent O(4) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 30°. In the fourth Ti site, Ti(4) is bonded to one O(1), one O(5), one O(6), one O(9), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 31°. There are nine inequivalent O sites. In the first O site, O(5) is bonded in a single-bond geometry to two equivalent Cs(2), four equivalent Cs(1), and one Ti(4) atom. In the second O site, O(6) is bonded in a distorted linear geometry to two equivalent Cs(1), one Ti(1), and one Ti(4) atom. In the third O site, O(7) is bonded to one Ti(3) and three equivalent Ti(2) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to one Ti(1) and two equivalent Ti(4) atoms. In the fifth O site, O(9) is bonded in a 4-coordinate geometry to two equivalent Cs(2), one Ti(3), and one Ti(4) atom. In the sixth O site, O(1) is bonded to one Ti(3), one Ti(4), and two equivalent Ti(1) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the seventh O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Cs(1), one Ti(1), and one Ti(2) atom. In the eighth O site, O(3) is bonded in a distorted water-like geometry to two equivalent Cs(2), one Ti(2), and one Ti(3) atom. In the ninth O site, O(4) is bonded to one Ti(1), one Ti(2), and two equivalent Ti(3) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. is represented by the CIF file [CIF]
data_Cs2Ti4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.828
_cell_length_b   10.352
_cell_length_c   12.101
_cell_angle_alpha   106.800
_cell_angle_beta   90.000
_cell_angle_gamma   100.653
_symmetry_Int_Tables_number   1
_cell_volume   450.396
_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  0.586  0.172  0.583  1.0
  Cs  Cs1  1  0.414  0.828  0.417  1.0
  Cs  Cs2  1  0.515  0.031  0.839  1.0
  Cs  Cs3  1  0.485  0.969  0.161  1.0
  Ti  Ti4  1  0.753  0.506  0.334  1.0
  Ti  Ti5  1  0.247  0.494  0.666  1.0
  Ti  Ti6  1  0.208  0.416  0.897  1.0
  Ti  Ti7  1  0.792  0.584  0.103  1.0
  Ti  Ti8  1  0.829  0.658  0.876  1.0
  Ti  Ti9  1  0.171  0.342  0.124  1.0
  Ti  Ti10  1  0.866  0.731  0.642  1.0
  Ti  Ti11  1  0.134  0.269  0.358  1.0
  O  O12  1  0.766  0.533  0.700  1.0
  O  O13  1  0.234  0.467  0.300  1.0
  O  O14  1  0.828  0.656  0.257  1.0
  O  O15  1  0.172  0.344  0.743  1.0
  O  O16  1  0.134  0.269  0.961  1.0
  O  O17  1  0.866  0.731  0.039  1.0
  O  O18  1  0.303  0.606  0.860  1.0
  O  O19  1  0.697  0.394  0.140  1.0
  O  O20  1  0.948  0.895  0.627  1.0
  O  O21  1  0.052  0.105  0.373  1.0
  O  O22  1  0.811  0.621  0.475  1.0
  O  O23  1  0.189  0.379  0.525  1.0
  O  O24  1  0.732  0.464  0.922  1.0
  O  O25  1  0.268  0.536  0.078  1.0
  O  O26  1  0.659  0.319  0.355  1.0
  O  O27  1  0.341  0.681  0.645  1.0
  O  O28  1  0.901  0.801  0.820  1.0
  O  O29  1  0.099  0.199  0.180  1.0
[/CIF]
.