The compound described by Ca5Ta4O15 crystallizes in the trigonal P-3m1 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 9-coordinate geometry to nine equivalent O(1) atoms. In the second Ca site, Ca(2) is bonded in a 9-coordinate geometry to three equivalent O(1) and six equivalent O(3) atoms. In the third Ca site, Ca(3) is bonded to six equivalent O(2) and six equivalent O(3) atoms to form CaO12 cuboctahedra that share corners with six equivalent Ca(3)O12 cuboctahedra, faces with two equivalent Ta(2)O6 octahedra, and faces with six equivalent Ta(1)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form TaO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, and faces with three equivalent Ca(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-10°. In the second Ta site, Ta(2) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form TaO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra and  a faceface with one Ca(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 10°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Ca(2), three equivalent Ca(1), and one Ta(2) atom. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ca(3) and two equivalent Ta(1) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ca(3), two equivalent Ca(2), one Ta(1), and one Ta(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca5Ta4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.633
_cell_length_b   5.633
_cell_length_c   11.502
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   316.042
_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
  Ca  Ca0  1  0.333  0.667  0.960  1.0
  Ca  Ca1  1  0.333  0.667  0.261  1.0
  Ca  Ca2  1  0.000  0.000  0.500  1.0
  Ca  Ca3  1  0.667  0.333  0.739  1.0
  Ca  Ca4  1  0.667  0.333  0.040  1.0
  Ta  Ta5  1  0.333  0.667  0.604  1.0
  Ta  Ta6  1  0.000  0.000  0.815  1.0
  Ta  Ta7  1  0.000  0.000  0.185  1.0
  Ta  Ta8  1  0.667  0.333  0.396  1.0
  O  O9  1  0.172  0.828  0.108  1.0
  O  O10  1  0.000  0.500  0.500  1.0
  O  O11  1  0.162  0.838  0.693  1.0
  O  O12  1  0.162  0.325  0.693  1.0
  O  O13  1  0.172  0.344  0.108  1.0
  O  O14  1  0.344  0.172  0.892  1.0
  O  O15  1  0.675  0.838  0.693  1.0
  O  O16  1  0.500  0.500  0.500  1.0
  O  O17  1  0.325  0.162  0.307  1.0
  O  O18  1  0.656  0.828  0.108  1.0
  O  O19  1  0.500  0.000  0.500  1.0
  O  O20  1  0.838  0.675  0.307  1.0
  O  O21  1  0.828  0.656  0.892  1.0
  O  O22  1  0.838  0.162  0.307  1.0
  O  O23  1  0.828  0.172  0.892  1.0
[/CIF]
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The compound described by Ca5Ta4O15 crystallizes in the trigonal P-3m1 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 9-coordinate geometry to nine equivalent O(1) atoms. In the second Ca site, Ca(2) is bonded in a 9-coordinate geometry to three equivalent O(1) and six equivalent O(3) atoms. In the third Ca site, Ca(3) is bonded to six equivalent O(2) and six equivalent O(3) atoms to form CaO12 cuboctahedra that share corners with six equivalent Ca(3)O12 cuboctahedra, faces with two equivalent Ta(2)O6 octahedra, and faces with six equivalent Ta(1)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form TaO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, and faces with three equivalent Ca(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-10°. In the second Ta site, Ta(2) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form TaO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra and  a faceface with one Ca(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 10°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Ca(2), three equivalent Ca(1), and one Ta(2) atom. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ca(3) and two equivalent Ta(1) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ca(3), two equivalent Ca(2), one Ta(1), and one Ta(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca5Ta4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.633
_cell_length_b   5.633
_cell_length_c   11.502
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   316.042
_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
  Ca  Ca0  1  0.333  0.667  0.960  1.0
  Ca  Ca1  1  0.333  0.667  0.261  1.0
  Ca  Ca2  1  0.000  0.000  0.500  1.0
  Ca  Ca3  1  0.667  0.333  0.739  1.0
  Ca  Ca4  1  0.667  0.333  0.040  1.0
  Ta  Ta5  1  0.333  0.667  0.604  1.0
  Ta  Ta6  1  0.000  0.000  0.815  1.0
  Ta  Ta7  1  0.000  0.000  0.185  1.0
  Ta  Ta8  1  0.667  0.333  0.396  1.0
  O  O9  1  0.172  0.828  0.108  1.0
  O  O10  1  0.000  0.500  0.500  1.0
  O  O11  1  0.162  0.838  0.693  1.0
  O  O12  1  0.162  0.325  0.693  1.0
  O  O13  1  0.172  0.344  0.108  1.0
  O  O14  1  0.344  0.172  0.892  1.0
  O  O15  1  0.675  0.838  0.693  1.0
  O  O16  1  0.500  0.500  0.500  1.0
  O  O17  1  0.325  0.162  0.307  1.0
  O  O18  1  0.656  0.828  0.108  1.0
  O  O19  1  0.500  0.000  0.500  1.0
  O  O20  1  0.838  0.675  0.307  1.0
  O  O21  1  0.828  0.656  0.892  1.0
  O  O22  1  0.838  0.162  0.307  1.0
  O  O23  1  0.828  0.172  0.892  1.0
[/CIF]
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