The crystal structure described by Rb8Ta6O19 crystallizes in the tetragonal I4/m space group. Rb(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(4), one O(5), and four equivalent O(2) atoms to form distorted corner-sharing TaO6 octahedra. The corner-sharing octahedra are not tilted. In the second Ta site, Ta(2) is bonded in a 6-coordinate geometry to one O(3), one O(5), two equivalent O(1), and two equivalent O(2) atoms. There are five inequivalent O sites. In the first O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Rb(1), one Ta(1), and one Ta(2) atom. In the second O site, O(3) is bonded in a distorted single-bond geometry to four equivalent Rb(1) and one Ta(2) atom. In the third O site, O(4) is bonded in a distorted single-bond geometry to four equivalent Rb(1) and one Ta(1) atom. In the fourth O site, O(5) is bonded in an octahedral geometry to two equivalent Ta(1) and four equivalent Ta(2) atoms. In the fifth O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Rb(1) and two equivalent Ta(2) atoms. is represented by the CIF file [CIF]
data_Rb8Ta6O19
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.631
_cell_length_b   9.631
_cell_length_c   9.631
_cell_angle_alpha   118.949
_cell_angle_beta   118.952
_cell_angle_gamma   91.827
_symmetry_Int_Tables_number   1
_cell_volume   641.344
_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
  Rb  Rb0  1  0.628  0.444  0.360  1.0
  Rb  Rb1  1  0.372  0.556  0.640  1.0
  Rb  Rb2  1  0.083  0.267  0.640  1.0
  Rb  Rb3  1  0.444  0.083  0.816  1.0
  Rb  Rb4  1  0.917  0.733  0.360  1.0
  Rb  Rb5  1  0.556  0.917  0.184  1.0
  Rb  Rb6  1  0.267  0.628  0.184  1.0
  Rb  Rb7  1  0.733  0.372  0.816  1.0
  Ta  Ta8  1  0.174  0.174  0.000  1.0
  Ta  Ta9  1  0.826  0.826  1.000  1.0
  Ta  Ta10  1  0.219  0.106  0.325  1.0
  Ta  Ta11  1  0.781  0.894  0.675  1.0
  Ta  Ta12  1  0.106  0.781  0.887  1.0
  Ta  Ta13  1  0.894  0.219  0.113  1.0
  O  O14  1  0.089  0.266  0.354  1.0
  O  O15  1  0.911  0.734  0.646  1.0
  O  O16  1  0.266  0.911  0.177  1.0
  O  O17  1  0.734  0.089  0.823  1.0
  O  O18  1  0.326  0.237  0.270  1.0
  O  O19  1  0.674  0.763  0.730  1.0
  O  O20  1  0.966  0.055  0.730  1.0
  O  O21  1  0.237  0.967  0.911  1.0
  O  O22  1  0.034  0.945  0.270  1.0
  O  O23  1  0.763  0.033  0.089  1.0
  O  O24  1  0.055  0.326  0.089  1.0
  O  O25  1  0.945  0.674  0.911  1.0
  O  O26  1  0.378  0.203  0.580  1.0
  O  O27  1  0.622  0.797  0.420  1.0
  O  O28  1  0.203  0.622  0.825  1.0
  O  O29  1  0.797  0.378  0.175  1.0
  O  O30  1  0.309  0.309  0.000  1.0
  O  O31  1  0.691  0.691  1.000  1.0
  O  O32  1  1.000  1.000  1.000  1.0
[/CIF]
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The crystal structure described by Rb8Ta6O19 crystallizes in the tetragonal I4/m space group. Rb(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(4), one O(5), and four equivalent O(2) atoms to form distorted corner-sharing TaO6 octahedra. The corner-sharing octahedra are not tilted. In the second Ta site, Ta(2) is bonded in a 6-coordinate geometry to one O(3), one O(5), two equivalent O(1), and two equivalent O(2) atoms. There are five inequivalent O sites. In the first O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Rb(1), one Ta(1), and one Ta(2) atom. In the second O site, O(3) is bonded in a distorted single-bond geometry to four equivalent Rb(1) and one Ta(2) atom. In the third O site, O(4) is bonded in a distorted single-bond geometry to four equivalent Rb(1) and one Ta(1) atom. In the fourth O site, O(5) is bonded in an octahedral geometry to two equivalent Ta(1) and four equivalent Ta(2) atoms. In the fifth O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Rb(1) and two equivalent Ta(2) atoms. is represented by the CIF file [CIF]
data_Rb8Ta6O19
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.631
_cell_length_b   9.631
_cell_length_c   9.631
_cell_angle_alpha   118.949
_cell_angle_beta   118.952
_cell_angle_gamma   91.827
_symmetry_Int_Tables_number   1
_cell_volume   641.344
_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
  Rb  Rb0  1  0.628  0.444  0.360  1.0
  Rb  Rb1  1  0.372  0.556  0.640  1.0
  Rb  Rb2  1  0.083  0.267  0.640  1.0
  Rb  Rb3  1  0.444  0.083  0.816  1.0
  Rb  Rb4  1  0.917  0.733  0.360  1.0
  Rb  Rb5  1  0.556  0.917  0.184  1.0
  Rb  Rb6  1  0.267  0.628  0.184  1.0
  Rb  Rb7  1  0.733  0.372  0.816  1.0
  Ta  Ta8  1  0.174  0.174  0.000  1.0
  Ta  Ta9  1  0.826  0.826  1.000  1.0
  Ta  Ta10  1  0.219  0.106  0.325  1.0
  Ta  Ta11  1  0.781  0.894  0.675  1.0
  Ta  Ta12  1  0.106  0.781  0.887  1.0
  Ta  Ta13  1  0.894  0.219  0.113  1.0
  O  O14  1  0.089  0.266  0.354  1.0
  O  O15  1  0.911  0.734  0.646  1.0
  O  O16  1  0.266  0.911  0.177  1.0
  O  O17  1  0.734  0.089  0.823  1.0
  O  O18  1  0.326  0.237  0.270  1.0
  O  O19  1  0.674  0.763  0.730  1.0
  O  O20  1  0.966  0.055  0.730  1.0
  O  O21  1  0.237  0.967  0.911  1.0
  O  O22  1  0.034  0.945  0.270  1.0
  O  O23  1  0.763  0.033  0.089  1.0
  O  O24  1  0.055  0.326  0.089  1.0
  O  O25  1  0.945  0.674  0.911  1.0
  O  O26  1  0.378  0.203  0.580  1.0
  O  O27  1  0.622  0.797  0.420  1.0
  O  O28  1  0.203  0.622  0.825  1.0
  O  O29  1  0.797  0.378  0.175  1.0
  O  O30  1  0.309  0.309  0.000  1.0
  O  O31  1  0.691  0.691  1.000  1.0
  O  O32  1  1.000  1.000  1.000  1.0
[/CIF]
.