The material structure described by Eu5Ta4O15 crystallizes in the trigonal P-3m1 space group. There are three inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form EuO12 cuboctahedra that share corners with six equivalent Eu(1)O12 cuboctahedra, faces with two equivalent Ta(2)O6 octahedra, and faces with six equivalent Ta(1)O6 octahedra. In the second Eu site, Eu(2) is bonded in a 12-coordinate geometry to three equivalent O(1), three equivalent O(3), and six equivalent O(2) atoms. In the third Eu site, Eu(3) is bonded in a 12-coordinate geometry to three equivalent O(2) and nine equivalent O(3) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) 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 Eu(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. In the second Ta site, Ta(2) 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 and  a faceface with one Eu(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 8°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Eu(1), two equivalent Eu(2), and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Eu(1), one Eu(3), two equivalent Eu(2), one Ta(1), and one Ta(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Eu(2), three equivalent Eu(3), and one Ta(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Eu5Ta4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.702
_cell_length_b   5.702
_cell_length_c   11.537
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   324.858
_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
  Eu  Eu0  1  0.000  0.000  0.000  1.0
  Eu  Eu1  1  0.667  0.333  0.231  1.0
  Eu  Eu2  1  0.333  0.667  0.769  1.0
  Eu  Eu3  1  0.667  0.333  0.561  1.0
  Eu  Eu4  1  0.333  0.667  0.439  1.0
  Ta  Ta5  1  0.667  0.333  0.896  1.0
  Ta  Ta6  1  0.333  0.667  0.104  1.0
  Ta  Ta7  1  0.000  0.000  0.680  1.0
  Ta  Ta8  1  0.000  0.000  0.320  1.0
  O  O9  1  0.500  0.000  0.000  1.0
  O  O10  1  0.500  0.500  0.000  1.0
  O  O11  1  0.000  0.500  0.000  1.0
  O  O12  1  0.329  0.165  0.803  1.0
  O  O13  1  0.835  0.671  0.803  1.0
  O  O14  1  0.835  0.165  0.803  1.0
  O  O15  1  0.671  0.835  0.197  1.0
  O  O16  1  0.165  0.329  0.197  1.0
  O  O17  1  0.165  0.835  0.197  1.0
  O  O18  1  0.341  0.170  0.396  1.0
  O  O19  1  0.830  0.659  0.396  1.0
  O  O20  1  0.830  0.170  0.396  1.0
  O  O21  1  0.659  0.830  0.604  1.0
  O  O22  1  0.170  0.341  0.604  1.0
  O  O23  1  0.170  0.830  0.604  1.0
[/CIF]
.
The material structure described by Eu5Ta4O15 crystallizes in the trigonal P-3m1 space group. There are three inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form EuO12 cuboctahedra that share corners with six equivalent Eu(1)O12 cuboctahedra, faces with two equivalent Ta(2)O6 octahedra, and faces with six equivalent Ta(1)O6 octahedra. In the second Eu site, Eu(2) is bonded in a 12-coordinate geometry to three equivalent O(1), three equivalent O(3), and six equivalent O(2) atoms. In the third Eu site, Eu(3) is bonded in a 12-coordinate geometry to three equivalent O(2) and nine equivalent O(3) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) 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 Eu(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. In the second Ta site, Ta(2) 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 and  a faceface with one Eu(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 8°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Eu(1), two equivalent Eu(2), and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Eu(1), one Eu(3), two equivalent Eu(2), one Ta(1), and one Ta(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Eu(2), three equivalent Eu(3), and one Ta(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Eu5Ta4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.702
_cell_length_b   5.702
_cell_length_c   11.537
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   324.858
_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
  Eu  Eu0  1  0.000  0.000  0.000  1.0
  Eu  Eu1  1  0.667  0.333  0.231  1.0
  Eu  Eu2  1  0.333  0.667  0.769  1.0
  Eu  Eu3  1  0.667  0.333  0.561  1.0
  Eu  Eu4  1  0.333  0.667  0.439  1.0
  Ta  Ta5  1  0.667  0.333  0.896  1.0
  Ta  Ta6  1  0.333  0.667  0.104  1.0
  Ta  Ta7  1  0.000  0.000  0.680  1.0
  Ta  Ta8  1  0.000  0.000  0.320  1.0
  O  O9  1  0.500  0.000  0.000  1.0
  O  O10  1  0.500  0.500  0.000  1.0
  O  O11  1  0.000  0.500  0.000  1.0
  O  O12  1  0.329  0.165  0.803  1.0
  O  O13  1  0.835  0.671  0.803  1.0
  O  O14  1  0.835  0.165  0.803  1.0
  O  O15  1  0.671  0.835  0.197  1.0
  O  O16  1  0.165  0.329  0.197  1.0
  O  O17  1  0.165  0.835  0.197  1.0
  O  O18  1  0.341  0.170  0.396  1.0
  O  O19  1  0.830  0.659  0.396  1.0
  O  O20  1  0.830  0.170  0.396  1.0
  O  O21  1  0.659  0.830  0.604  1.0
  O  O22  1  0.170  0.341  0.604  1.0
  O  O23  1  0.170  0.830  0.604  1.0
[/CIF]
.