The crystal structure described by Ca3Ta2O8 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(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 Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Ta(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted edge-sharing TaO6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 tetrahedra that share corners with four equivalent O(3)Ca3Ta trigonal pyramids, edges with two equivalent O(1)Ca2Ta2 tetrahedra, and  an edgeedge with one O(3)Ca3Ta trigonal pyramid. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Ta(1) atom. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and one Ta(1) atom to form distorted OCa3Ta trigonal pyramids that share corners with four equivalent O(1)Ca2Ta2 tetrahedra,  a cornercorner with one O(3)Ca3Ta trigonal pyramid,  an edgeedge with one O(1)Ca2Ta2 tetrahedra, and  an edgeedge with one O(3)Ca3Ta trigonal pyramid. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Ca(2) and two equivalent Ta(1) atoms. is represented by the CIF file [CIF]
data_Ca3Ta2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.712
_cell_length_b   6.712
_cell_length_c   9.175
_cell_angle_alpha   72.597
_cell_angle_beta   72.597
_cell_angle_gamma   82.837
_symmetry_Int_Tables_number   1
_cell_volume   376.064
_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  0.604  0.734  0.500  1.0
  Ca  Ca1  1  0.724  0.276  0.750  1.0
  Ca  Ca2  1  0.266  0.396  0.000  1.0
  Ca  Ca3  1  0.734  0.604  1.000  1.0
  Ca  Ca4  1  0.276  0.724  0.250  1.0
  Ca  Ca5  1  0.396  0.266  0.500  1.0
  Ta  Ta6  1  0.218  0.934  0.879  1.0
  Ta  Ta7  1  0.934  0.218  0.379  1.0
  Ta  Ta8  1  0.066  0.782  0.621  1.0
  Ta  Ta9  1  0.782  0.066  0.121  1.0
  O  O10  1  0.061  0.691  0.856  1.0
  O  O11  1  0.691  0.061  0.356  1.0
  O  O12  1  0.821  0.625  0.679  1.0
  O  O13  1  0.401  0.717  0.969  1.0
  O  O14  1  0.945  0.107  0.888  1.0
  O  O15  1  0.625  0.821  0.179  1.0
  O  O16  1  0.717  0.401  0.469  1.0
  O  O17  1  0.893  0.055  0.612  1.0
  O  O18  1  0.107  0.945  0.388  1.0
  O  O19  1  0.283  0.599  0.531  1.0
  O  O20  1  0.375  0.179  0.821  1.0
  O  O21  1  0.055  0.893  0.112  1.0
  O  O22  1  0.599  0.283  0.031  1.0
  O  O23  1  0.179  0.375  0.321  1.0
  O  O24  1  0.309  0.939  0.644  1.0
  O  O25  1  0.939  0.309  0.144  1.0
[/CIF]
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The crystal structure described by Ca3Ta2O8 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(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 Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Ta(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted edge-sharing TaO6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 tetrahedra that share corners with four equivalent O(3)Ca3Ta trigonal pyramids, edges with two equivalent O(1)Ca2Ta2 tetrahedra, and  an edgeedge with one O(3)Ca3Ta trigonal pyramid. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Ta(1) atom. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and one Ta(1) atom to form distorted OCa3Ta trigonal pyramids that share corners with four equivalent O(1)Ca2Ta2 tetrahedra,  a cornercorner with one O(3)Ca3Ta trigonal pyramid,  an edgeedge with one O(1)Ca2Ta2 tetrahedra, and  an edgeedge with one O(3)Ca3Ta trigonal pyramid. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Ca(2) and two equivalent Ta(1) atoms. is represented by the CIF file [CIF]
data_Ca3Ta2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.712
_cell_length_b   6.712
_cell_length_c   9.175
_cell_angle_alpha   72.597
_cell_angle_beta   72.597
_cell_angle_gamma   82.837
_symmetry_Int_Tables_number   1
_cell_volume   376.064
_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  0.604  0.734  0.500  1.0
  Ca  Ca1  1  0.724  0.276  0.750  1.0
  Ca  Ca2  1  0.266  0.396  0.000  1.0
  Ca  Ca3  1  0.734  0.604  1.000  1.0
  Ca  Ca4  1  0.276  0.724  0.250  1.0
  Ca  Ca5  1  0.396  0.266  0.500  1.0
  Ta  Ta6  1  0.218  0.934  0.879  1.0
  Ta  Ta7  1  0.934  0.218  0.379  1.0
  Ta  Ta8  1  0.066  0.782  0.621  1.0
  Ta  Ta9  1  0.782  0.066  0.121  1.0
  O  O10  1  0.061  0.691  0.856  1.0
  O  O11  1  0.691  0.061  0.356  1.0
  O  O12  1  0.821  0.625  0.679  1.0
  O  O13  1  0.401  0.717  0.969  1.0
  O  O14  1  0.945  0.107  0.888  1.0
  O  O15  1  0.625  0.821  0.179  1.0
  O  O16  1  0.717  0.401  0.469  1.0
  O  O17  1  0.893  0.055  0.612  1.0
  O  O18  1  0.107  0.945  0.388  1.0
  O  O19  1  0.283  0.599  0.531  1.0
  O  O20  1  0.375  0.179  0.821  1.0
  O  O21  1  0.055  0.893  0.112  1.0
  O  O22  1  0.599  0.283  0.031  1.0
  O  O23  1  0.179  0.375  0.321  1.0
  O  O24  1  0.309  0.939  0.644  1.0
  O  O25  1  0.939  0.309  0.144  1.0
[/CIF]
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