The structure described by Ca2Ta2WO8 crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 4-coordinate geometry to one O(6), one O(8), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to one O(1), one O(5), one O(7), and two equivalent O(6) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(8) atom to form distorted TaO6 octahedra that share corners with two equivalent W(1)O6 octahedra, corners with two equivalent W(2)O6 octahedra, and edges with two equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(8) atom to form distorted TaO6 octahedra that share corners with two equivalent W(1)O6 octahedra, corners with two equivalent W(2)O6 octahedra, and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-53°. There are two inequivalent W sites. In the first W site, W(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form WO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent W(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form WO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. There are eight inequivalent O sites. In the first O site, O(7) is bonded to one Ca(2), two equivalent Ca(1), and one Ta(1) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the second O site, O(8) is bonded in a 3-coordinate geometry to one Ca(1), one Ta(1), and one Ta(2) atom. In the third O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Ta(1), one Ta(2), and one W(2) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one W(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ta(1), one W(1), and one W(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ta(2), one W(1), and one W(2) atom. In the seventh O site, O(5) is bonded in a 3-coordinate geometry to one Ca(2), one Ta(1), and one Ta(2) atom. In the eighth O site, O(6) is bonded to one Ca(1), two equivalent Ca(2), and one Ta(2) atom to form a mixture of distorted edge and corner-sharing OCa3Ta tetrahedra. is represented by the CIF file [CIF]
data_Ca2Ta2WO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.123
_cell_length_b   10.123
_cell_length_c   5.529
_cell_angle_alpha   87.303
_cell_angle_beta   87.303
_cell_angle_gamma   36.684
_symmetry_Int_Tables_number   1
_cell_volume   338.066
_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
  Ca  Ca0  1  0.878  0.546  0.517  1.0
  Ca  Ca1  1  0.454  0.122  0.483  1.0
  Ca  Ca2  1  0.120  0.475  0.988  1.0
  Ca  Ca3  1  0.525  0.880  0.012  1.0
  Ta  Ta4  1  0.017  0.759  0.508  1.0
  Ta  Ta5  1  0.241  0.983  0.492  1.0
  Ta  Ta6  1  0.976  0.256  0.014  1.0
  Ta  Ta7  1  0.744  0.024  0.986  1.0
  W  W8  1  0.635  0.365  0.500  1.0
  W  W9  1  0.368  0.632  0.000  1.0
  O  O10  1  0.077  0.772  0.855  1.0
  O  O11  1  0.228  0.923  0.145  1.0
  O  O12  1  0.944  0.187  0.674  1.0
  O  O13  1  0.813  0.056  0.326  1.0
  O  O14  1  0.307  0.583  0.353  1.0
  O  O15  1  0.417  0.693  0.647  1.0
  O  O16  1  0.690  0.425  0.153  1.0
  O  O17  1  0.575  0.310  0.847  1.0
  O  O18  1  0.881  0.767  0.234  1.0
  O  O19  1  0.233  0.119  0.766  1.0
  O  O20  1  0.470  0.153  0.080  1.0
  O  O21  1  0.847  0.530  0.920  1.0
  O  O22  1  0.524  0.846  0.416  1.0
  O  O23  1  0.154  0.476  0.584  1.0
  O  O24  1  0.756  0.878  0.728  1.0
  O  O25  1  0.122  0.244  0.272  1.0
[/CIF]
.
The structure described by Ca2Ta2WO8 crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 4-coordinate geometry to one O(6), one O(8), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to one O(1), one O(5), one O(7), and two equivalent O(6) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(8) atom to form distorted TaO6 octahedra that share corners with two equivalent W(1)O6 octahedra, corners with two equivalent W(2)O6 octahedra, and edges with two equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(8) atom to form distorted TaO6 octahedra that share corners with two equivalent W(1)O6 octahedra, corners with two equivalent W(2)O6 octahedra, and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-53°. There are two inequivalent W sites. In the first W site, W(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form WO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent W(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form WO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent W(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-51°. There are eight inequivalent O sites. In the first O site, O(7) is bonded to one Ca(2), two equivalent Ca(1), and one Ta(1) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the second O site, O(8) is bonded in a 3-coordinate geometry to one Ca(1), one Ta(1), and one Ta(2) atom. In the third O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Ta(1), one Ta(2), and one W(2) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one W(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ta(1), one W(1), and one W(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ta(2), one W(1), and one W(2) atom. In the seventh O site, O(5) is bonded in a 3-coordinate geometry to one Ca(2), one Ta(1), and one Ta(2) atom. In the eighth O site, O(6) is bonded to one Ca(1), two equivalent Ca(2), and one Ta(2) atom to form a mixture of distorted edge and corner-sharing OCa3Ta tetrahedra. is represented by the CIF file [CIF]
data_Ca2Ta2WO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.123
_cell_length_b   10.123
_cell_length_c   5.529
_cell_angle_alpha   87.303
_cell_angle_beta   87.303
_cell_angle_gamma   36.684
_symmetry_Int_Tables_number   1
_cell_volume   338.066
_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
  Ca  Ca0  1  0.878  0.546  0.517  1.0
  Ca  Ca1  1  0.454  0.122  0.483  1.0
  Ca  Ca2  1  0.120  0.475  0.988  1.0
  Ca  Ca3  1  0.525  0.880  0.012  1.0
  Ta  Ta4  1  0.017  0.759  0.508  1.0
  Ta  Ta5  1  0.241  0.983  0.492  1.0
  Ta  Ta6  1  0.976  0.256  0.014  1.0
  Ta  Ta7  1  0.744  0.024  0.986  1.0
  W  W8  1  0.635  0.365  0.500  1.0
  W  W9  1  0.368  0.632  0.000  1.0
  O  O10  1  0.077  0.772  0.855  1.0
  O  O11  1  0.228  0.923  0.145  1.0
  O  O12  1  0.944  0.187  0.674  1.0
  O  O13  1  0.813  0.056  0.326  1.0
  O  O14  1  0.307  0.583  0.353  1.0
  O  O15  1  0.417  0.693  0.647  1.0
  O  O16  1  0.690  0.425  0.153  1.0
  O  O17  1  0.575  0.310  0.847  1.0
  O  O18  1  0.881  0.767  0.234  1.0
  O  O19  1  0.233  0.119  0.766  1.0
  O  O20  1  0.470  0.153  0.080  1.0
  O  O21  1  0.847  0.530  0.920  1.0
  O  O22  1  0.524  0.846  0.416  1.0
  O  O23  1  0.154  0.476  0.584  1.0
  O  O24  1  0.756  0.878  0.728  1.0
  O  O25  1  0.122  0.244  0.272  1.0
[/CIF]
.