The structure described by Na2Ca3Ta2O9 crystallizes in the trigonal R32 space group. Na(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. In the second Ca site, Ca(2) is bonded in a distorted octahedral geometry to six equivalent O(1) atoms. Ta(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Na(1), one Ca(1), one Ca(2), and one Ta(1) atom. In the second O site, O(2) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form a mixture of distorted edge and corner-sharing OCa2Ta2 trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Ca3Ta2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.822
_cell_length_b   8.822
_cell_length_c   8.822
_cell_angle_alpha   37.614
_cell_angle_beta   37.614
_cell_angle_gamma   37.614
_symmetry_Int_Tables_number   1
_cell_volume   229.438
_cell_formula_units_Z   1
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
  Na  Na0  1  0.200  0.200  0.200  1.0
  Na  Na1  1  0.800  0.800  0.800  1.0
  Ca  Ca2  1  0.371  0.371  0.371  1.0
  Ca  Ca3  1  0.500  0.500  0.500  1.0
  Ca  Ca4  1  0.629  0.629  0.629  1.0
  Ta  Ta5  1  0.064  0.064  0.064  1.0
  Ta  Ta6  1  0.936  0.936  0.936  1.0
  O  O7  1  0.343  0.187  0.787  1.0
  O  O8  1  0.813  0.657  0.213  1.0
  O  O9  1  0.787  0.343  0.187  1.0
  O  O10  1  0.213  0.813  0.657  1.0
  O  O11  1  0.187  0.787  0.343  1.0
  O  O12  1  0.258  0.000  0.742  1.0
  O  O13  1  0.742  0.258  0.000  1.0
  O  O14  1  0.000  0.742  0.258  1.0
  O  O15  1  0.657  0.213  0.813  1.0
[/CIF]
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The structure described by Na2Ca3Ta2O9 crystallizes in the trigonal R32 space group. Na(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. In the second Ca site, Ca(2) is bonded in a distorted octahedral geometry to six equivalent O(1) atoms. Ta(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Na(1), one Ca(1), one Ca(2), and one Ta(1) atom. In the second O site, O(2) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form a mixture of distorted edge and corner-sharing OCa2Ta2 trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Ca3Ta2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.822
_cell_length_b   8.822
_cell_length_c   8.822
_cell_angle_alpha   37.614
_cell_angle_beta   37.614
_cell_angle_gamma   37.614
_symmetry_Int_Tables_number   1
_cell_volume   229.438
_cell_formula_units_Z   1
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
  Na  Na0  1  0.200  0.200  0.200  1.0
  Na  Na1  1  0.800  0.800  0.800  1.0
  Ca  Ca2  1  0.371  0.371  0.371  1.0
  Ca  Ca3  1  0.500  0.500  0.500  1.0
  Ca  Ca4  1  0.629  0.629  0.629  1.0
  Ta  Ta5  1  0.064  0.064  0.064  1.0
  Ta  Ta6  1  0.936  0.936  0.936  1.0
  O  O7  1  0.343  0.187  0.787  1.0
  O  O8  1  0.813  0.657  0.213  1.0
  O  O9  1  0.787  0.343  0.187  1.0
  O  O10  1  0.213  0.813  0.657  1.0
  O  O11  1  0.187  0.787  0.343  1.0
  O  O12  1  0.258  0.000  0.742  1.0
  O  O13  1  0.742  0.258  0.000  1.0
  O  O14  1  0.000  0.742  0.258  1.0
  O  O15  1  0.657  0.213  0.813  1.0
[/CIF]
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