The material described by Ca2Ta2CuO8 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(5), and two equivalent O(8) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(5), one O(8), two equivalent O(6), and two equivalent O(7) 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(6), and one O(8) atom to form distorted edge-sharing TaO6 octahedra. 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(7) atom to form distorted edge-sharing TaO6 octahedra. Cu(1) is bonded in a see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one Cu(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one Cu(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ta(1) and one Cu(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Ta(2) and one Cu(1) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Ta(1), and one Ta(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Ta(1), and one Ta(2) atom. In the seventh O site, O(7) is bonded to one Ca(1), two equivalent Ca(2), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OCa3Ta trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(2), two equivalent Ca(1), and one Ta(1) atom to form a mixture of distorted corner and edge-sharing OCa3Ta trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Ta2CuO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.403
_cell_length_b   6.712
_cell_length_c   9.999
_cell_angle_alpha   108.729
_cell_angle_beta   92.846
_cell_angle_gamma   90.629
_symmetry_Int_Tables_number   1
_cell_volume   342.896
_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  0.756  0.458  0.586  1.0
  Ca  Ca1  1  0.744  0.872  0.416  1.0
  Ca  Ca2  1  0.244  0.542  0.414  1.0
  Ca  Ca3  1  0.256  0.128  0.584  1.0
  Ta  Ta4  1  0.734  0.261  0.230  1.0
  Ta  Ta5  1  0.767  0.024  0.769  1.0
  Ta  Ta6  1  0.266  0.739  0.770  1.0
  Ta  Ta7  1  0.233  0.976  0.231  1.0
  Cu  Cu8  1  0.749  0.697  1.000  1.0
  Cu  Cu9  1  0.251  0.303  0.000  1.0
  O  O10  1  0.065  0.198  0.146  1.0
  O  O11  1  0.440  0.038  0.855  1.0
  O  O12  1  0.935  0.802  0.854  1.0
  O  O13  1  0.560  0.962  0.145  1.0
  O  O14  1  0.544  0.386  0.118  1.0
  O  O15  1  0.964  0.255  0.880  1.0
  O  O16  1  0.456  0.614  0.882  1.0
  O  O17  1  0.036  0.745  0.120  1.0
  O  O18  1  0.476  0.251  0.370  1.0
  O  O19  1  0.024  0.878  0.631  1.0
  O  O20  1  0.332  0.848  0.371  1.0
  O  O21  1  0.168  0.473  0.629  1.0
  O  O22  1  0.668  0.152  0.629  1.0
  O  O23  1  0.832  0.527  0.371  1.0
  O  O24  1  0.976  0.122  0.369  1.0
  O  O25  1  0.524  0.749  0.630  1.0
[/CIF]
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The material described by Ca2Ta2CuO8 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(5), and two equivalent O(8) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(5), one O(8), two equivalent O(6), and two equivalent O(7) 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(6), and one O(8) atom to form distorted edge-sharing TaO6 octahedra. 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(7) atom to form distorted edge-sharing TaO6 octahedra. Cu(1) is bonded in a see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one Cu(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one Cu(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ta(1) and one Cu(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Ta(2) and one Cu(1) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Ta(1), and one Ta(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Ta(1), and one Ta(2) atom. In the seventh O site, O(7) is bonded to one Ca(1), two equivalent Ca(2), and one Ta(2) atom to form a mixture of distorted corner and edge-sharing OCa3Ta trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(2), two equivalent Ca(1), and one Ta(1) atom to form a mixture of distorted corner and edge-sharing OCa3Ta trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Ta2CuO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.403
_cell_length_b   6.712
_cell_length_c   9.999
_cell_angle_alpha   108.729
_cell_angle_beta   92.846
_cell_angle_gamma   90.629
_symmetry_Int_Tables_number   1
_cell_volume   342.896
_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  0.756  0.458  0.586  1.0
  Ca  Ca1  1  0.744  0.872  0.416  1.0
  Ca  Ca2  1  0.244  0.542  0.414  1.0
  Ca  Ca3  1  0.256  0.128  0.584  1.0
  Ta  Ta4  1  0.734  0.261  0.230  1.0
  Ta  Ta5  1  0.767  0.024  0.769  1.0
  Ta  Ta6  1  0.266  0.739  0.770  1.0
  Ta  Ta7  1  0.233  0.976  0.231  1.0
  Cu  Cu8  1  0.749  0.697  1.000  1.0
  Cu  Cu9  1  0.251  0.303  0.000  1.0
  O  O10  1  0.065  0.198  0.146  1.0
  O  O11  1  0.440  0.038  0.855  1.0
  O  O12  1  0.935  0.802  0.854  1.0
  O  O13  1  0.560  0.962  0.145  1.0
  O  O14  1  0.544  0.386  0.118  1.0
  O  O15  1  0.964  0.255  0.880  1.0
  O  O16  1  0.456  0.614  0.882  1.0
  O  O17  1  0.036  0.745  0.120  1.0
  O  O18  1  0.476  0.251  0.370  1.0
  O  O19  1  0.024  0.878  0.631  1.0
  O  O20  1  0.332  0.848  0.371  1.0
  O  O21  1  0.168  0.473  0.629  1.0
  O  O22  1  0.668  0.152  0.629  1.0
  O  O23  1  0.832  0.527  0.371  1.0
  O  O24  1  0.976  0.122  0.369  1.0
  O  O25  1  0.524  0.749  0.630  1.0
[/CIF]
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