The crystal structure described by Ca2Ta2FeO8 crystallizes in the monoclinic C2 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), two equivalent O(6), and two equivalent O(8) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(8), two equivalent O(5), 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 TaO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-54°. 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 TaO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-55°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-54°. In the second Fe site, Fe(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-55°. There are eight inequivalent O sites. In the first 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 second 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. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one Fe(1) 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 Fe(2) atom. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Ta(1), one Fe(1), and one Fe(2) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Ta(2), one Fe(1), and one Fe(2) atom. In the seventh O site, O(5) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Ta(1), and one Ta(2) atom. In the eighth O site, O(6) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Ta(1), and one Ta(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Ta2FeO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.444
_cell_length_b   6.477
_cell_length_c   10.062
_cell_angle_alpha   108.759
_cell_angle_beta   91.964
_cell_angle_gamma   90.007
_symmetry_Int_Tables_number   1
_cell_volume   335.710
_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  0.581  1.0
  Ca  Ca1  1  0.744  0.876  0.418  1.0
  Ca  Ca2  1  0.244  0.540  0.418  1.0
  Ca  Ca3  1  0.255  0.122  0.581  1.0
  Ta  Ta4  1  0.743  0.258  0.226  1.0
  Ta  Ta5  1  0.756  0.032  0.773  1.0
  Ta  Ta6  1  0.256  0.741  0.773  1.0
  Ta  Ta7  1  0.243  0.966  0.226  1.0
  Fe  Fe8  1  0.250  0.354  0.999  1.0
  Fe  Fe9  1  0.750  0.643  1.000  1.0
  O  O10  1  0.074  0.189  0.142  1.0
  O  O11  1  0.425  0.047  0.858  1.0
  O  O12  1  0.925  0.809  0.857  1.0
  O  O13  1  0.574  0.951  0.142  1.0
  O  O14  1  0.575  0.404  0.116  1.0
  O  O15  1  0.924  0.287  0.883  1.0
  O  O16  1  0.424  0.594  0.883  1.0
  O  O17  1  0.075  0.710  0.116  1.0
  O  O18  1  0.484  0.245  0.365  1.0
  O  O19  1  0.016  0.881  0.634  1.0
  O  O20  1  0.984  0.117  0.365  1.0
  O  O21  1  0.516  0.753  0.635  1.0
  O  O22  1  0.338  0.843  0.371  1.0
  O  O23  1  0.161  0.472  0.628  1.0
  O  O24  1  0.661  0.155  0.628  1.0
  O  O25  1  0.838  0.526  0.371  1.0
[/CIF]
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The crystal structure described by Ca2Ta2FeO8 crystallizes in the monoclinic C2 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), two equivalent O(6), and two equivalent O(8) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(8), two equivalent O(5), 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 TaO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-54°. 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 TaO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-55°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-54°. In the second Fe site, Fe(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-55°. There are eight inequivalent O sites. In the first 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 second 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. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(2), and one Fe(1) 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 Fe(2) atom. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Ta(1), one Fe(1), and one Fe(2) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Ta(2), one Fe(1), and one Fe(2) atom. In the seventh O site, O(5) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Ta(1), and one Ta(2) atom. In the eighth O site, O(6) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Ta(1), and one Ta(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Ta2FeO8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.444
_cell_length_b   6.477
_cell_length_c   10.062
_cell_angle_alpha   108.759
_cell_angle_beta   91.964
_cell_angle_gamma   90.007
_symmetry_Int_Tables_number   1
_cell_volume   335.710
_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  0.581  1.0
  Ca  Ca1  1  0.744  0.876  0.418  1.0
  Ca  Ca2  1  0.244  0.540  0.418  1.0
  Ca  Ca3  1  0.255  0.122  0.581  1.0
  Ta  Ta4  1  0.743  0.258  0.226  1.0
  Ta  Ta5  1  0.756  0.032  0.773  1.0
  Ta  Ta6  1  0.256  0.741  0.773  1.0
  Ta  Ta7  1  0.243  0.966  0.226  1.0
  Fe  Fe8  1  0.250  0.354  0.999  1.0
  Fe  Fe9  1  0.750  0.643  1.000  1.0
  O  O10  1  0.074  0.189  0.142  1.0
  O  O11  1  0.425  0.047  0.858  1.0
  O  O12  1  0.925  0.809  0.857  1.0
  O  O13  1  0.574  0.951  0.142  1.0
  O  O14  1  0.575  0.404  0.116  1.0
  O  O15  1  0.924  0.287  0.883  1.0
  O  O16  1  0.424  0.594  0.883  1.0
  O  O17  1  0.075  0.710  0.116  1.0
  O  O18  1  0.484  0.245  0.365  1.0
  O  O19  1  0.016  0.881  0.634  1.0
  O  O20  1  0.984  0.117  0.365  1.0
  O  O21  1  0.516  0.753  0.635  1.0
  O  O22  1  0.338  0.843  0.371  1.0
  O  O23  1  0.161  0.472  0.628  1.0
  O  O24  1  0.661  0.155  0.628  1.0
  O  O25  1  0.838  0.526  0.371  1.0
[/CIF]
.