The crystal structure described by Eu2Ta2O7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. In the second Eu site, Eu(2) is bonded to one O(2), three equivalent O(4), four equivalent O(3), and four equivalent O(5) atoms to form EuO12 cuboctahedra that share corners with six equivalent Eu(2)O12 cuboctahedra, faces with four equivalent Eu(2)O12 cuboctahedra, faces with two equivalent Ta(1)O6 octahedra, and faces with six equivalent Ta(2)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Eu(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 9-14°. In the second Ta site, Ta(2) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) 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 six equivalent Eu(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-12°. There are five inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Eu(1) and one Ta(1) atom to form a mixture of distorted corner and edge-sharing OEu3Ta tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Eu(2) and two equivalent Ta(1) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Eu(2), one Ta(1), and one Ta(2) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to three equivalent Eu(2) and two equivalent Ta(2) atoms. In the fifth O site, O(5) is bonded in a distorted linear geometry to four equivalent Eu(2) and two equivalent Ta(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Eu2Ta2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.823
_cell_length_b   13.823
_cell_length_c   5.711
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   163.425
_symmetry_Int_Tables_number   1
_cell_volume   311.285
_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
  Eu  Eu0  1  0.715  0.285  0.750  1.0
  Eu  Eu1  1  0.285  0.715  0.250  1.0
  Eu  Eu2  1  0.554  0.446  0.250  1.0
  Eu  Eu3  1  0.446  0.554  0.750  1.0
  Ta  Ta4  1  0.159  0.841  0.250  1.0
  Ta  Ta5  1  0.841  0.159  0.750  1.0
  Ta  Ta6  1  0.054  0.946  0.750  1.0
  Ta  Ta7  1  0.946  0.054  0.250  1.0
  O  O8  1  0.208  0.792  0.491  1.0
  O  O9  1  0.792  0.208  0.509  1.0
  O  O10  1  0.208  0.792  0.009  1.0
  O  O11  1  0.792  0.208  0.991  1.0
  O  O12  1  0.650  0.350  0.250  1.0
  O  O13  1  0.350  0.650  0.750  1.0
  O  O14  1  0.100  0.900  0.491  1.0
  O  O15  1  0.900  0.100  0.509  1.0
  O  O16  1  0.100  0.900  0.009  1.0
  O  O17  1  0.900  0.100  0.991  1.0
  O  O18  1  0.546  0.454  0.750  1.0
  O  O19  1  0.454  0.546  0.250  1.0
  O  O20  1  0.000  0.000  0.500  1.0
  O  O21  1  0.000  0.000  0.000  1.0
[/CIF]
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The crystal structure described by Eu2Ta2O7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. In the second Eu site, Eu(2) is bonded to one O(2), three equivalent O(4), four equivalent O(3), and four equivalent O(5) atoms to form EuO12 cuboctahedra that share corners with six equivalent Eu(2)O12 cuboctahedra, faces with four equivalent Eu(2)O12 cuboctahedra, faces with two equivalent Ta(1)O6 octahedra, and faces with six equivalent Ta(2)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Eu(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 9-14°. In the second Ta site, Ta(2) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) 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 six equivalent Eu(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-12°. There are five inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Eu(1) and one Ta(1) atom to form a mixture of distorted corner and edge-sharing OEu3Ta tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Eu(2) and two equivalent Ta(1) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Eu(2), one Ta(1), and one Ta(2) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to three equivalent Eu(2) and two equivalent Ta(2) atoms. In the fifth O site, O(5) is bonded in a distorted linear geometry to four equivalent Eu(2) and two equivalent Ta(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Eu2Ta2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.823
_cell_length_b   13.823
_cell_length_c   5.711
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   163.425
_symmetry_Int_Tables_number   1
_cell_volume   311.285
_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
  Eu  Eu0  1  0.715  0.285  0.750  1.0
  Eu  Eu1  1  0.285  0.715  0.250  1.0
  Eu  Eu2  1  0.554  0.446  0.250  1.0
  Eu  Eu3  1  0.446  0.554  0.750  1.0
  Ta  Ta4  1  0.159  0.841  0.250  1.0
  Ta  Ta5  1  0.841  0.159  0.750  1.0
  Ta  Ta6  1  0.054  0.946  0.750  1.0
  Ta  Ta7  1  0.946  0.054  0.250  1.0
  O  O8  1  0.208  0.792  0.491  1.0
  O  O9  1  0.792  0.208  0.509  1.0
  O  O10  1  0.208  0.792  0.009  1.0
  O  O11  1  0.792  0.208  0.991  1.0
  O  O12  1  0.650  0.350  0.250  1.0
  O  O13  1  0.350  0.650  0.750  1.0
  O  O14  1  0.100  0.900  0.491  1.0
  O  O15  1  0.900  0.100  0.509  1.0
  O  O16  1  0.100  0.900  0.009  1.0
  O  O17  1  0.900  0.100  0.991  1.0
  O  O18  1  0.546  0.454  0.750  1.0
  O  O19  1  0.454  0.546  0.250  1.0
  O  O20  1  0.000  0.000  0.500  1.0
  O  O21  1  0.000  0.000  0.000  1.0
[/CIF]
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