The crystal structure described by Sr4Ta2O9 crystallizes in the triclinic P-1 space group. There are five inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. In the second Sr site, Sr(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(9) atoms to form SrO6 octahedra that share corners with six equivalent Ta(2)O6 octahedra and corners with six equivalent Sr(4)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 33-34°. In the third Sr site, Sr(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(8) atoms to form SrO6 octahedra that share corners with six equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-36°. In the fourth Sr site, Sr(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted SrO6 pentagonal pyramids that share corners with three equivalent Sr(2)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, and edges with three equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-70°. In the fifth Sr site, Sr(5) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted TaO6 octahedra that share corners with three equivalent Sr(3)O6 octahedra, corners with three equivalent Sr(4)O6 pentagonal pyramids, and  a faceface with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-36°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted TaO6 octahedra that share corners with three equivalent Sr(2)O6 octahedra, edges with three equivalent Sr(4)O6 pentagonal pyramids, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 33-34°. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1), one Sr(4), one Sr(5), one Ta(1), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OSr3Ta2 trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Sr(4), and one Ta(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(3), one Sr(5), and one Ta(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Sr(4), and one Ta(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(3), one Sr(5), and one Ta(1) atom. In the sixth O site, O(6) is bonded to one Sr(1), one Sr(4), one Sr(5), one Ta(1), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OSr3Ta2 trigonal bipyramids. In the seventh O site, O(7) is bonded to one Sr(1), one Sr(4), one Sr(5), one Ta(1), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OSr3Ta2 trigonal bipyramids. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(3), one Sr(5), and one Ta(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Sr(4), and one Ta(2) atom. is represented by the CIF card [CIF]
data_Sr4Ta2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.949
_cell_length_b   5.954
_cell_length_c   15.841
_cell_angle_alpha   89.946
_cell_angle_beta   89.965
_cell_angle_gamma   60.041
_symmetry_Int_Tables_number   1
_cell_volume   486.200
_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
  Sr  Sr0  1  0.999  0.002  0.256  1.0
  Sr  Sr1  1  0.000  0.000  0.500  1.0
  Sr  Sr2  1  0.000  0.000  0.000  1.0
  Sr  Sr3  1  0.666  0.669  0.356  1.0
  Sr  Sr4  1  0.667  0.664  0.132  1.0
  Sr  Sr5  1  0.333  0.336  0.868  1.0
  Sr  Sr6  1  0.334  0.331  0.644  1.0
  Sr  Sr7  1  0.001  0.998  0.744  1.0
  Ta  Ta8  1  0.665  0.670  0.850  1.0
  Ta  Ta9  1  0.667  0.665  0.660  1.0
  Ta  Ta10  1  0.333  0.335  0.340  1.0
  Ta  Ta11  1  0.335  0.330  0.150  1.0
  O  O12  1  0.595  0.959  0.753  1.0
  O  O13  1  0.919  0.730  0.607  1.0
  O  O14  1  0.921  0.727  0.901  1.0
  O  O15  1  0.349  0.916  0.607  1.0
  O  O16  1  0.355  0.927  0.902  1.0
  O  O17  1  0.958  0.445  0.754  1.0
  O  O18  1  0.446  0.595  0.754  1.0
  O  O19  1  0.283  0.635  0.094  1.0
  O  O20  1  0.267  0.653  0.393  1.0
  O  O21  1  0.733  0.347  0.607  1.0
  O  O22  1  0.717  0.365  0.906  1.0
  O  O23  1  0.554  0.405  0.246  1.0
  O  O24  1  0.042  0.555  0.246  1.0
  O  O25  1  0.645  0.073  0.098  1.0
  O  O26  1  0.651  0.084  0.393  1.0
  O  O27  1  0.079  0.273  0.099  1.0
  O  O28  1  0.081  0.270  0.393  1.0
  O  O29  1  0.405  0.041  0.247  1.0
[/CIF]
.
The crystal structure described by Sr4Ta2O9 crystallizes in the triclinic P-1 space group. There are five inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. In the second Sr site, Sr(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(9) atoms to form SrO6 octahedra that share corners with six equivalent Ta(2)O6 octahedra and corners with six equivalent Sr(4)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 33-34°. In the third Sr site, Sr(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(8) atoms to form SrO6 octahedra that share corners with six equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-36°. In the fourth Sr site, Sr(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted SrO6 pentagonal pyramids that share corners with three equivalent Sr(2)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, and edges with three equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-70°. In the fifth Sr site, Sr(5) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted TaO6 octahedra that share corners with three equivalent Sr(3)O6 octahedra, corners with three equivalent Sr(4)O6 pentagonal pyramids, and  a faceface with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-36°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted TaO6 octahedra that share corners with three equivalent Sr(2)O6 octahedra, edges with three equivalent Sr(4)O6 pentagonal pyramids, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 33-34°. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Sr(1), one Sr(4), one Sr(5), one Ta(1), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OSr3Ta2 trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Sr(4), and one Ta(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(3), one Sr(5), and one Ta(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Sr(4), and one Ta(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(3), one Sr(5), and one Ta(1) atom. In the sixth O site, O(6) is bonded to one Sr(1), one Sr(4), one Sr(5), one Ta(1), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OSr3Ta2 trigonal bipyramids. In the seventh O site, O(7) is bonded to one Sr(1), one Sr(4), one Sr(5), one Ta(1), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OSr3Ta2 trigonal bipyramids. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(3), one Sr(5), and one Ta(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Sr(4), and one Ta(2) atom. is represented by the CIF card [CIF]
data_Sr4Ta2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.949
_cell_length_b   5.954
_cell_length_c   15.841
_cell_angle_alpha   89.946
_cell_angle_beta   89.965
_cell_angle_gamma   60.041
_symmetry_Int_Tables_number   1
_cell_volume   486.200
_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
  Sr  Sr0  1  0.999  0.002  0.256  1.0
  Sr  Sr1  1  0.000  0.000  0.500  1.0
  Sr  Sr2  1  0.000  0.000  0.000  1.0
  Sr  Sr3  1  0.666  0.669  0.356  1.0
  Sr  Sr4  1  0.667  0.664  0.132  1.0
  Sr  Sr5  1  0.333  0.336  0.868  1.0
  Sr  Sr6  1  0.334  0.331  0.644  1.0
  Sr  Sr7  1  0.001  0.998  0.744  1.0
  Ta  Ta8  1  0.665  0.670  0.850  1.0
  Ta  Ta9  1  0.667  0.665  0.660  1.0
  Ta  Ta10  1  0.333  0.335  0.340  1.0
  Ta  Ta11  1  0.335  0.330  0.150  1.0
  O  O12  1  0.595  0.959  0.753  1.0
  O  O13  1  0.919  0.730  0.607  1.0
  O  O14  1  0.921  0.727  0.901  1.0
  O  O15  1  0.349  0.916  0.607  1.0
  O  O16  1  0.355  0.927  0.902  1.0
  O  O17  1  0.958  0.445  0.754  1.0
  O  O18  1  0.446  0.595  0.754  1.0
  O  O19  1  0.283  0.635  0.094  1.0
  O  O20  1  0.267  0.653  0.393  1.0
  O  O21  1  0.733  0.347  0.607  1.0
  O  O22  1  0.717  0.365  0.906  1.0
  O  O23  1  0.554  0.405  0.246  1.0
  O  O24  1  0.042  0.555  0.246  1.0
  O  O25  1  0.645  0.073  0.098  1.0
  O  O26  1  0.651  0.084  0.393  1.0
  O  O27  1  0.079  0.273  0.099  1.0
  O  O28  1  0.081  0.270  0.393  1.0
  O  O29  1  0.405  0.041  0.247  1.0
[/CIF]
.