The crystal structure described by Sr3Ta2O8 crystallizes in the monoclinic C2/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Sr site, Sr(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted SrO6 pentagonal pyramids that share corners with four equivalent Ta(1)O6 octahedra and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles are 36°. Ta(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted TaO6 octahedra that share corners with two equivalent Sr(2)O6 pentagonal pyramids, edges with two equivalent Ta(1)O6 octahedra, and  an edgeedge with one Sr(2)O6 pentagonal pyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1) and two equivalent Ta(1) atoms to form distorted edge-sharing OSr2Ta2 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Sr(2), two equivalent Sr(1), and one Ta(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(2), two equivalent Sr(1), and one Ta(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Sr(2) and two equivalent Ta(1) atoms. is represented by the CIF file [CIF]
data_Sr3Ta2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.988
_cell_length_b   6.988
_cell_length_c   9.436
_cell_angle_alpha   72.933
_cell_angle_beta   72.933
_cell_angle_gamma   82.435
_symmetry_Int_Tables_number   1
_cell_volume   420.595
_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  0.615  0.737  0.497  1.0
  Sr  Sr1  1  0.724  0.276  0.750  1.0
  Sr  Sr2  1  0.263  0.385  0.003  1.0
  Sr  Sr3  1  0.737  0.615  0.997  1.0
  Sr  Sr4  1  0.276  0.724  0.250  1.0
  Sr  Sr5  1  0.385  0.263  0.503  1.0
  Ta  Ta6  1  0.209  0.929  0.880  1.0
  Ta  Ta7  1  0.929  0.209  0.380  1.0
  Ta  Ta8  1  0.071  0.791  0.620  1.0
  Ta  Ta9  1  0.791  0.071  0.120  1.0
  O  O10  1  0.065  0.703  0.851  1.0
  O  O11  1  0.703  0.065  0.351  1.0
  O  O12  1  0.839  0.634  0.680  1.0
  O  O13  1  0.391  0.723  0.965  1.0
  O  O14  1  0.945  0.101  0.892  1.0
  O  O15  1  0.634  0.839  0.180  1.0
  O  O16  1  0.723  0.391  0.465  1.0
  O  O17  1  0.899  0.055  0.608  1.0
  O  O18  1  0.101  0.945  0.392  1.0
  O  O19  1  0.277  0.609  0.535  1.0
  O  O20  1  0.366  0.161  0.820  1.0
  O  O21  1  0.055  0.899  0.108  1.0
  O  O22  1  0.609  0.277  0.035  1.0
  O  O23  1  0.161  0.366  0.320  1.0
  O  O24  1  0.297  0.935  0.649  1.0
  O  O25  1  0.935  0.297  0.149  1.0
[/CIF]
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The crystal structure described by Sr3Ta2O8 crystallizes in the monoclinic C2/c space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Sr site, Sr(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted SrO6 pentagonal pyramids that share corners with four equivalent Ta(1)O6 octahedra and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles are 36°. Ta(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted TaO6 octahedra that share corners with two equivalent Sr(2)O6 pentagonal pyramids, edges with two equivalent Ta(1)O6 octahedra, and  an edgeedge with one Sr(2)O6 pentagonal pyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1) and two equivalent Ta(1) atoms to form distorted edge-sharing OSr2Ta2 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Sr(2), two equivalent Sr(1), and one Ta(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(2), two equivalent Sr(1), and one Ta(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Sr(2) and two equivalent Ta(1) atoms. is represented by the CIF file [CIF]
data_Sr3Ta2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.988
_cell_length_b   6.988
_cell_length_c   9.436
_cell_angle_alpha   72.933
_cell_angle_beta   72.933
_cell_angle_gamma   82.435
_symmetry_Int_Tables_number   1
_cell_volume   420.595
_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  0.615  0.737  0.497  1.0
  Sr  Sr1  1  0.724  0.276  0.750  1.0
  Sr  Sr2  1  0.263  0.385  0.003  1.0
  Sr  Sr3  1  0.737  0.615  0.997  1.0
  Sr  Sr4  1  0.276  0.724  0.250  1.0
  Sr  Sr5  1  0.385  0.263  0.503  1.0
  Ta  Ta6  1  0.209  0.929  0.880  1.0
  Ta  Ta7  1  0.929  0.209  0.380  1.0
  Ta  Ta8  1  0.071  0.791  0.620  1.0
  Ta  Ta9  1  0.791  0.071  0.120  1.0
  O  O10  1  0.065  0.703  0.851  1.0
  O  O11  1  0.703  0.065  0.351  1.0
  O  O12  1  0.839  0.634  0.680  1.0
  O  O13  1  0.391  0.723  0.965  1.0
  O  O14  1  0.945  0.101  0.892  1.0
  O  O15  1  0.634  0.839  0.180  1.0
  O  O16  1  0.723  0.391  0.465  1.0
  O  O17  1  0.899  0.055  0.608  1.0
  O  O18  1  0.101  0.945  0.392  1.0
  O  O19  1  0.277  0.609  0.535  1.0
  O  O20  1  0.366  0.161  0.820  1.0
  O  O21  1  0.055  0.899  0.108  1.0
  O  O22  1  0.609  0.277  0.035  1.0
  O  O23  1  0.161  0.366  0.320  1.0
  O  O24  1  0.297  0.935  0.649  1.0
  O  O25  1  0.935  0.297  0.149  1.0
[/CIF]
.