The compound described by Ca3(CaTa2)O9 crystallizes in the triclinic P-1 space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom. In the second Ca site, Ca(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(9) atoms to form CaO6 octahedra that share corners with six equivalent Ca(4)O6 octahedra and corners with six equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-62°. In the third Ca site, Ca(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(8) atoms to form CaO6 octahedra that share corners with six equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 35-37°. In the fourth Ca site, Ca(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted CaO6 octahedra that share corners with three equivalent Ca(2)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, and edges with three equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-62°. In the fifth Ca site, Ca(5) is bonded in a distorted trigonal planar geometry to one O(3), one O(5), one O(7), and one O(8) atom. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form TaO6 octahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and  a faceface with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-37°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted TaO6 octahedra that share corners with three equivalent Ca(2)O6 octahedra, edges with three equivalent Ca(4)O6 octahedra, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-42°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(4), one Ta(1), and one Ta(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one Ta(1) atom. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom to form distorted corner-sharing OCa3Ta trigonal pyramids. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one Ta(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(4), one Ta(1), and one Ta(2) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(4), one Ca(5), one Ta(1), and one Ta(2) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one Ta(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom. is represented by the CIF card [CIF]
data_Ca4Ta2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.761
_cell_length_b   5.762
_cell_length_c   14.873
_cell_angle_alpha   89.905
_cell_angle_beta   90.200
_cell_angle_gamma   119.954
_symmetry_Int_Tables_number   1
_cell_volume   427.793
_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  0.001  0.998  0.255  1.0
  Ca  Ca1  1  0.000  0.000  0.500  1.0
  Ca  Ca2  1  0.000  0.000  0.000  1.0
  Ca  Ca3  1  0.334  0.667  0.344  1.0
  Ca  Ca4  1  0.340  0.667  0.095  1.0
  Ca  Ca5  1  0.660  0.333  0.905  1.0
  Ca  Ca6  1  0.666  0.333  0.656  1.0
  Ca  Ca7  1  0.999  0.002  0.745  1.0
  Ta  Ta8  1  0.328  0.665  0.849  1.0
  Ta  Ta9  1  0.333  0.667  0.649  1.0
  Ta  Ta10  1  0.667  0.333  0.351  1.0
  Ta  Ta11  1  0.672  0.335  0.151  1.0
  O  O12  1  0.039  0.619  0.752  1.0
  O  O13  1  0.294  0.948  0.599  1.0
  O  O14  1  0.283  0.932  0.910  1.0
  O  O15  1  0.051  0.344  0.600  1.0
  O  O16  1  0.060  0.354  0.911  1.0
  O  O17  1  0.575  0.957  0.753  1.0
  O  O18  1  0.382  0.423  0.754  1.0
  O  O19  1  0.366  0.291  0.085  1.0
  O  O20  1  0.347  0.294  0.401  1.0
  O  O21  1  0.653  0.706  0.599  1.0
  O  O22  1  0.634  0.709  0.915  1.0
  O  O23  1  0.618  0.577  0.246  1.0
  O  O24  1  0.425  0.043  0.247  1.0
  O  O25  1  0.940  0.646  0.089  1.0
  O  O26  1  0.949  0.656  0.400  1.0
  O  O27  1  0.717  0.068  0.090  1.0
  O  O28  1  0.706  0.052  0.401  1.0
  O  O29  1  0.961  0.381  0.248  1.0
[/CIF]
.
The compound described by Ca3(CaTa2)O9 crystallizes in the triclinic P-1 space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom. In the second Ca site, Ca(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(9) atoms to form CaO6 octahedra that share corners with six equivalent Ca(4)O6 octahedra and corners with six equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-62°. In the third Ca site, Ca(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(8) atoms to form CaO6 octahedra that share corners with six equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 35-37°. In the fourth Ca site, Ca(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted CaO6 octahedra that share corners with three equivalent Ca(2)O6 octahedra, corners with three equivalent Ta(1)O6 octahedra, and edges with three equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-62°. In the fifth Ca site, Ca(5) is bonded in a distorted trigonal planar geometry to one O(3), one O(5), one O(7), and one O(8) atom. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form TaO6 octahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and  a faceface with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-37°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form distorted TaO6 octahedra that share corners with three equivalent Ca(2)O6 octahedra, edges with three equivalent Ca(4)O6 octahedra, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-42°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(4), one Ta(1), and one Ta(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one Ta(1) atom. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom to form distorted corner-sharing OCa3Ta trigonal pyramids. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one Ta(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(4), one Ta(1), and one Ta(2) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(4), one Ca(5), one Ta(1), and one Ta(2) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one Ta(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom. is represented by the CIF card [CIF]
data_Ca4Ta2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.761
_cell_length_b   5.762
_cell_length_c   14.873
_cell_angle_alpha   89.905
_cell_angle_beta   90.200
_cell_angle_gamma   119.954
_symmetry_Int_Tables_number   1
_cell_volume   427.793
_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  0.001  0.998  0.255  1.0
  Ca  Ca1  1  0.000  0.000  0.500  1.0
  Ca  Ca2  1  0.000  0.000  0.000  1.0
  Ca  Ca3  1  0.334  0.667  0.344  1.0
  Ca  Ca4  1  0.340  0.667  0.095  1.0
  Ca  Ca5  1  0.660  0.333  0.905  1.0
  Ca  Ca6  1  0.666  0.333  0.656  1.0
  Ca  Ca7  1  0.999  0.002  0.745  1.0
  Ta  Ta8  1  0.328  0.665  0.849  1.0
  Ta  Ta9  1  0.333  0.667  0.649  1.0
  Ta  Ta10  1  0.667  0.333  0.351  1.0
  Ta  Ta11  1  0.672  0.335  0.151  1.0
  O  O12  1  0.039  0.619  0.752  1.0
  O  O13  1  0.294  0.948  0.599  1.0
  O  O14  1  0.283  0.932  0.910  1.0
  O  O15  1  0.051  0.344  0.600  1.0
  O  O16  1  0.060  0.354  0.911  1.0
  O  O17  1  0.575  0.957  0.753  1.0
  O  O18  1  0.382  0.423  0.754  1.0
  O  O19  1  0.366  0.291  0.085  1.0
  O  O20  1  0.347  0.294  0.401  1.0
  O  O21  1  0.653  0.706  0.599  1.0
  O  O22  1  0.634  0.709  0.915  1.0
  O  O23  1  0.618  0.577  0.246  1.0
  O  O24  1  0.425  0.043  0.247  1.0
  O  O25  1  0.940  0.646  0.089  1.0
  O  O26  1  0.949  0.656  0.400  1.0
  O  O27  1  0.717  0.068  0.090  1.0
  O  O28  1  0.706  0.052  0.401  1.0
  O  O29  1  0.961  0.381  0.248  1.0
[/CIF]
.