The crystal structure described by Na2Ca2Ta3O10 crystallizes in the tetragonal I4/mmm space group. Na(1) is bonded in a 5-coordinate geometry to five equivalent O(2) atoms. Ca(1) is bonded to four equivalent O(1), four equivalent O(3), and four equivalent O(4) atoms to form CaO12 cuboctahedra that share corners with eight equivalent Ca(1)O12 cuboctahedra, faces with five equivalent Ca(1)O12 cuboctahedra, faces with four equivalent Ta(1)O6 octahedra, and faces with four equivalent Ta(2)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form distorted TaO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, and faces with four equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-17°. In the second Ta site, Ta(2) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and faces with eight equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Ca(1), one Ta(1), and one Ta(2) atom. In the second O site, O(2) is bonded to five equivalent Na(1) and one Ta(1) atom to form a mixture of distorted corner and edge-sharing ONa5Ta octahedra. The corner-sharing octahedral tilt angles are 4°. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ca(1) and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to four equivalent Ca(1) and two equivalent Ta(2) atoms. is represented by the CIF file [CIF]
data_Na2Ca2Ta3O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.635
_cell_length_b   14.635
_cell_length_c   14.635
_cell_angle_alpha   164.335
_cell_angle_beta   164.335
_cell_angle_gamma   22.223
_symmetry_Int_Tables_number   1
_cell_volume   228.459
_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  0.712  0.712  0.000  1.0
  Na  Na1  1  0.288  0.288  0.000  1.0
  Ca  Ca2  1  0.576  0.576  0.000  1.0
  Ca  Ca3  1  0.424  0.424  0.000  1.0
  Ta  Ta4  1  0.856  0.856  0.000  1.0
  Ta  Ta5  1  0.144  0.144  0.000  1.0
  Ta  Ta6  1  0.000  0.000  0.000  1.0
  O  O7  1  0.068  0.068  0.000  1.0
  O  O8  1  0.208  0.208  0.000  1.0
  O  O9  1  0.932  0.932  0.000  1.0
  O  O10  1  0.633  0.133  0.500  1.0
  O  O11  1  0.133  0.633  0.500  1.0
  O  O12  1  0.867  0.367  0.500  1.0
  O  O13  1  0.792  0.792  0.000  1.0
  O  O14  1  0.367  0.867  0.500  1.0
  O  O15  1  0.500  0.000  0.500  1.0
  O  O16  1  0.000  0.500  0.500  1.0
[/CIF]
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The crystal structure described by Na2Ca2Ta3O10 crystallizes in the tetragonal I4/mmm space group. Na(1) is bonded in a 5-coordinate geometry to five equivalent O(2) atoms. Ca(1) is bonded to four equivalent O(1), four equivalent O(3), and four equivalent O(4) atoms to form CaO12 cuboctahedra that share corners with eight equivalent Ca(1)O12 cuboctahedra, faces with five equivalent Ca(1)O12 cuboctahedra, faces with four equivalent Ta(1)O6 octahedra, and faces with four equivalent Ta(2)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form distorted TaO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, and faces with four equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-17°. In the second Ta site, Ta(2) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and faces with eight equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Ca(1), one Ta(1), and one Ta(2) atom. In the second O site, O(2) is bonded to five equivalent Na(1) and one Ta(1) atom to form a mixture of distorted corner and edge-sharing ONa5Ta octahedra. The corner-sharing octahedral tilt angles are 4°. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ca(1) and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to four equivalent Ca(1) and two equivalent Ta(2) atoms. is represented by the CIF file [CIF]
data_Na2Ca2Ta3O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.635
_cell_length_b   14.635
_cell_length_c   14.635
_cell_angle_alpha   164.335
_cell_angle_beta   164.335
_cell_angle_gamma   22.223
_symmetry_Int_Tables_number   1
_cell_volume   228.459
_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  0.712  0.712  0.000  1.0
  Na  Na1  1  0.288  0.288  0.000  1.0
  Ca  Ca2  1  0.576  0.576  0.000  1.0
  Ca  Ca3  1  0.424  0.424  0.000  1.0
  Ta  Ta4  1  0.856  0.856  0.000  1.0
  Ta  Ta5  1  0.144  0.144  0.000  1.0
  Ta  Ta6  1  0.000  0.000  0.000  1.0
  O  O7  1  0.068  0.068  0.000  1.0
  O  O8  1  0.208  0.208  0.000  1.0
  O  O9  1  0.932  0.932  0.000  1.0
  O  O10  1  0.633  0.133  0.500  1.0
  O  O11  1  0.133  0.633  0.500  1.0
  O  O12  1  0.867  0.367  0.500  1.0
  O  O13  1  0.792  0.792  0.000  1.0
  O  O14  1  0.367  0.867  0.500  1.0
  O  O15  1  0.500  0.000  0.500  1.0
  O  O16  1  0.000  0.500  0.500  1.0
[/CIF]
.