The structure described by Pb2Ta2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 2-20°. In the second Ta site, Ta(2) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(7) atoms to form distorted corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 2-20°. There are two inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(5) atoms. In the second Pb site, Pb(2) is bonded in a 6-coordinate geometry to one O(6), one O(7), two equivalent O(1), and two equivalent O(2) atoms. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ta(1), one Ta(2), and two equivalent Pb(2) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ta(2) and two equivalent Pb(2) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ta(1) and three equivalent Pb(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to one Ta(1) and one Ta(2) atom. In the fifth O site, O(5) is bonded to one Ta(1) and three equivalent Pb(1) atoms to form distorted corner-sharing OTaPb3 tetrahedra. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to two equivalent Ta(1) and one Pb(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to two equivalent Ta(2) and one Pb(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta2Pb2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.635
_cell_length_b   13.635
_cell_length_c   5.818
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   163.232
_symmetry_Int_Tables_number   1
_cell_volume   312.036
_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
  Ta  Ta0  1  0.839  0.161  0.749  1.0
  Ta  Ta1  1  0.944  0.056  0.251  1.0
  Ta  Ta2  1  0.161  0.839  0.249  1.0
  Ta  Ta3  1  0.056  0.944  0.751  1.0
  Pb  Pb4  1  0.712  0.288  0.756  1.0
  Pb  Pb5  1  0.556  0.444  0.273  1.0
  Pb  Pb6  1  0.288  0.712  0.256  1.0
  Pb  Pb7  1  0.444  0.556  0.773  1.0
  O  O8  1  0.902  0.098  0.963  1.0
  O  O9  1  0.998  0.002  0.467  1.0
  O  O10  1  0.792  0.208  0.986  1.0
  O  O11  1  0.894  0.106  0.474  1.0
  O  O12  1  0.788  0.212  0.524  1.0
  O  O13  1  0.651  0.349  0.241  1.0
  O  O14  1  0.551  0.449  0.711  1.0
  O  O15  1  0.212  0.788  0.024  1.0
  O  O16  1  0.449  0.551  0.211  1.0
  O  O17  1  0.349  0.651  0.741  1.0
  O  O18  1  0.098  0.902  0.463  1.0
  O  O19  1  0.106  0.894  0.974  1.0
  O  O20  1  0.002  0.998  0.967  1.0
  O  O21  1  0.208  0.792  0.486  1.0
[/CIF]
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The structure described by Pb2Ta2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 2-20°. In the second Ta site, Ta(2) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(7) atoms to form distorted corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 2-20°. There are two inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(5) atoms. In the second Pb site, Pb(2) is bonded in a 6-coordinate geometry to one O(6), one O(7), two equivalent O(1), and two equivalent O(2) atoms. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ta(1), one Ta(2), and two equivalent Pb(2) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ta(2) and two equivalent Pb(2) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ta(1) and three equivalent Pb(1) atoms. In the fourth O site, O(4) is bonded in a linear geometry to one Ta(1) and one Ta(2) atom. In the fifth O site, O(5) is bonded to one Ta(1) and three equivalent Pb(1) atoms to form distorted corner-sharing OTaPb3 tetrahedra. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to two equivalent Ta(1) and one Pb(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to two equivalent Ta(2) and one Pb(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta2Pb2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.635
_cell_length_b   13.635
_cell_length_c   5.818
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   163.232
_symmetry_Int_Tables_number   1
_cell_volume   312.036
_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
  Ta  Ta0  1  0.839  0.161  0.749  1.0
  Ta  Ta1  1  0.944  0.056  0.251  1.0
  Ta  Ta2  1  0.161  0.839  0.249  1.0
  Ta  Ta3  1  0.056  0.944  0.751  1.0
  Pb  Pb4  1  0.712  0.288  0.756  1.0
  Pb  Pb5  1  0.556  0.444  0.273  1.0
  Pb  Pb6  1  0.288  0.712  0.256  1.0
  Pb  Pb7  1  0.444  0.556  0.773  1.0
  O  O8  1  0.902  0.098  0.963  1.0
  O  O9  1  0.998  0.002  0.467  1.0
  O  O10  1  0.792  0.208  0.986  1.0
  O  O11  1  0.894  0.106  0.474  1.0
  O  O12  1  0.788  0.212  0.524  1.0
  O  O13  1  0.651  0.349  0.241  1.0
  O  O14  1  0.551  0.449  0.711  1.0
  O  O15  1  0.212  0.788  0.024  1.0
  O  O16  1  0.449  0.551  0.211  1.0
  O  O17  1  0.349  0.651  0.741  1.0
  O  O18  1  0.098  0.902  0.463  1.0
  O  O19  1  0.106  0.894  0.974  1.0
  O  O20  1  0.002  0.998  0.967  1.0
  O  O21  1  0.208  0.792  0.486  1.0
[/CIF]
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