The material described by Ba3SrNb2O9 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, faces with six equivalent Ba(2)O9 cuboctahedra, faces with two equivalent Sr(1)O6 octahedra, and faces with six equivalent Nb(1)O6 octahedra. In the second Ba site, Ba(2) is bonded to three equivalent O(2) and six equivalent O(1) atoms to form distorted BaO9 cuboctahedra that share corners with nine equivalent Ba(2)O9 cuboctahedra, edges with three equivalent Sr(1)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Nb(1)O6 octahedra. Sr(1) is bonded to six equivalent O(1) atoms to form SrO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra, edges with six equivalent Ba(2)O9 cuboctahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 8°. Nb(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with three equivalent Sr(1)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ba(2)O9 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1), two equivalent Ba(2), one Sr(1), and one Nb(1) atom. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Nb(1) atoms to form a mixture of distorted corner and face-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. is represented by the CIF file [CIF]
data_Ba3SrNb2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.049
_cell_length_b   6.049
_cell_length_c   7.699
_cell_angle_alpha   90.000
_cell_angle_beta   89.999
_cell_angle_gamma   119.999
_symmetry_Int_Tables_number   1
_cell_volume   244.013
_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
  Ba  Ba0  1  0.000  0.000  0.000  1.0
  Ba  Ba1  1  0.333  0.667  0.700  1.0
  Ba  Ba2  1  0.667  0.333  0.300  1.0
  Sr  Sr3  1  0.000  0.000  0.500  1.0
  Nb  Nb4  1  0.333  0.667  0.168  1.0
  Nb  Nb5  1  0.667  0.333  0.832  1.0
  O  O6  1  0.646  0.823  0.301  1.0
  O  O7  1  0.177  0.823  0.301  1.0
  O  O8  1  0.177  0.354  0.301  1.0
  O  O9  1  0.354  0.177  0.699  1.0
  O  O10  1  0.823  0.177  0.699  1.0
  O  O11  1  0.823  0.646  0.699  1.0
  O  O12  1  0.500  0.500  0.000  1.0
  O  O13  1  0.500  0.000  0.000  1.0
  O  O14  1  0.000  0.500  0.000  1.0
[/CIF]
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The material described by Ba3SrNb2O9 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, faces with six equivalent Ba(2)O9 cuboctahedra, faces with two equivalent Sr(1)O6 octahedra, and faces with six equivalent Nb(1)O6 octahedra. In the second Ba site, Ba(2) is bonded to three equivalent O(2) and six equivalent O(1) atoms to form distorted BaO9 cuboctahedra that share corners with nine equivalent Ba(2)O9 cuboctahedra, edges with three equivalent Sr(1)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Nb(1)O6 octahedra. Sr(1) is bonded to six equivalent O(1) atoms to form SrO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra, edges with six equivalent Ba(2)O9 cuboctahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 8°. Nb(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with three equivalent Sr(1)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ba(2)O9 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1), two equivalent Ba(2), one Sr(1), and one Nb(1) atom. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Nb(1) atoms to form a mixture of distorted corner and face-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. is represented by the CIF file [CIF]
data_Ba3SrNb2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.049
_cell_length_b   6.049
_cell_length_c   7.699
_cell_angle_alpha   90.000
_cell_angle_beta   89.999
_cell_angle_gamma   119.999
_symmetry_Int_Tables_number   1
_cell_volume   244.013
_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
  Ba  Ba0  1  0.000  0.000  0.000  1.0
  Ba  Ba1  1  0.333  0.667  0.700  1.0
  Ba  Ba2  1  0.667  0.333  0.300  1.0
  Sr  Sr3  1  0.000  0.000  0.500  1.0
  Nb  Nb4  1  0.333  0.667  0.168  1.0
  Nb  Nb5  1  0.667  0.333  0.832  1.0
  O  O6  1  0.646  0.823  0.301  1.0
  O  O7  1  0.177  0.823  0.301  1.0
  O  O8  1  0.177  0.354  0.301  1.0
  O  O9  1  0.354  0.177  0.699  1.0
  O  O10  1  0.823  0.177  0.699  1.0
  O  O11  1  0.823  0.646  0.699  1.0
  O  O12  1  0.500  0.500  0.000  1.0
  O  O13  1  0.500  0.000  0.000  1.0
  O  O14  1  0.000  0.500  0.000  1.0
[/CIF]
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