The structure described by Nd2Ta6O19 crystallizes in the hexagonal P6_3/mcm space group. Nd(1) is bonded to six equivalent O(4) atoms to form distorted edge-sharing NdO6 octahedra. Ta(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(4) is bonded in a trigonal planar geometry to two equivalent Nd(1) and one Ta(1) atom. In the second O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Ta(1) atoms. In the third O site, O(2) is bonded in a trigonal planar geometry to three equivalent Ta(1) atoms. In the fourth O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Ta(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nd2Ta6O19
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.463
_cell_length_b   6.463
_cell_length_c   20.578
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   744.407
_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
  Nd  Nd0  1  0.667  0.333  0.000  1.0
  Nd  Nd1  1  0.333  0.667  0.000  1.0
  Nd  Nd2  1  0.333  0.667  0.500  1.0
  Nd  Nd3  1  0.667  0.333  0.500  1.0
  Ta  Ta4  1  0.655  0.655  0.843  1.0
  Ta  Ta5  1  0.345  0.345  0.157  1.0
  Ta  Ta6  1  0.000  0.345  0.843  1.0
  Ta  Ta7  1  0.345  0.345  0.343  1.0
  Ta  Ta8  1  0.000  0.345  0.657  1.0
  Ta  Ta9  1  0.000  0.655  0.157  1.0
  Ta  Ta10  1  0.655  0.655  0.657  1.0
  Ta  Ta11  1  0.000  0.655  0.343  1.0
  Ta  Ta12  1  0.345  0.000  0.843  1.0
  Ta  Ta13  1  0.655  0.000  0.157  1.0
  Ta  Ta14  1  0.655  0.000  0.343  1.0
  Ta  Ta15  1  0.345  0.000  0.657  1.0
  O  O16  1  0.598  0.598  0.750  1.0
  O  O17  1  0.402  0.402  0.250  1.0
  O  O18  1  0.000  0.402  0.750  1.0
  O  O19  1  0.000  0.598  0.250  1.0
  O  O20  1  0.402  0.000  0.750  1.0
  O  O21  1  0.598  0.000  0.250  1.0
  O  O22  1  0.667  0.333  0.843  1.0
  O  O23  1  0.333  0.667  0.157  1.0
  O  O24  1  0.333  0.667  0.343  1.0
  O  O25  1  0.333  0.667  0.657  1.0
  O  O26  1  0.667  0.333  0.657  1.0
  O  O27  1  0.667  0.333  0.343  1.0
  O  O28  1  0.667  0.333  0.157  1.0
  O  O29  1  0.333  0.667  0.843  1.0
  O  O30  1  0.768  0.768  0.343  1.0
  O  O31  1  0.232  0.232  0.657  1.0
  O  O32  1  0.000  0.232  0.343  1.0
  O  O33  1  0.232  0.232  0.843  1.0
  O  O34  1  0.000  0.232  0.157  1.0
  O  O35  1  0.000  0.768  0.657  1.0
  O  O36  1  0.768  0.768  0.157  1.0
  O  O37  1  0.000  0.768  0.843  1.0
  O  O38  1  0.232  0.000  0.343  1.0
  O  O39  1  0.768  0.000  0.657  1.0
  O  O40  1  0.768  0.000  0.843  1.0
  O  O41  1  0.232  0.000  0.157  1.0
  O  O42  1  0.596  0.596  0.936  1.0
  O  O43  1  0.404  0.404  0.064  1.0
  O  O44  1  0.000  0.404  0.936  1.0
  O  O45  1  0.404  0.404  0.436  1.0
  O  O46  1  0.000  0.404  0.564  1.0
  O  O47  1  0.000  0.596  0.064  1.0
  O  O48  1  0.596  0.596  0.564  1.0
  O  O49  1  0.000  0.596  0.436  1.0
  O  O50  1  0.404  0.000  0.936  1.0
  O  O51  1  0.596  0.000  0.064  1.0
  O  O52  1  0.596  0.000  0.436  1.0
  O  O53  1  0.404  0.000  0.564  1.0
[/CIF]
.
The structure described by Nd2Ta6O19 crystallizes in the hexagonal P6_3/mcm space group. Nd(1) is bonded to six equivalent O(4) atoms to form distorted edge-sharing NdO6 octahedra. Ta(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(4) is bonded in a trigonal planar geometry to two equivalent Nd(1) and one Ta(1) atom. In the second O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Ta(1) atoms. In the third O site, O(2) is bonded in a trigonal planar geometry to three equivalent Ta(1) atoms. In the fourth O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Ta(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nd2Ta6O19
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.463
_cell_length_b   6.463
_cell_length_c   20.578
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   744.407
_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
  Nd  Nd0  1  0.667  0.333  0.000  1.0
  Nd  Nd1  1  0.333  0.667  0.000  1.0
  Nd  Nd2  1  0.333  0.667  0.500  1.0
  Nd  Nd3  1  0.667  0.333  0.500  1.0
  Ta  Ta4  1  0.655  0.655  0.843  1.0
  Ta  Ta5  1  0.345  0.345  0.157  1.0
  Ta  Ta6  1  0.000  0.345  0.843  1.0
  Ta  Ta7  1  0.345  0.345  0.343  1.0
  Ta  Ta8  1  0.000  0.345  0.657  1.0
  Ta  Ta9  1  0.000  0.655  0.157  1.0
  Ta  Ta10  1  0.655  0.655  0.657  1.0
  Ta  Ta11  1  0.000  0.655  0.343  1.0
  Ta  Ta12  1  0.345  0.000  0.843  1.0
  Ta  Ta13  1  0.655  0.000  0.157  1.0
  Ta  Ta14  1  0.655  0.000  0.343  1.0
  Ta  Ta15  1  0.345  0.000  0.657  1.0
  O  O16  1  0.598  0.598  0.750  1.0
  O  O17  1  0.402  0.402  0.250  1.0
  O  O18  1  0.000  0.402  0.750  1.0
  O  O19  1  0.000  0.598  0.250  1.0
  O  O20  1  0.402  0.000  0.750  1.0
  O  O21  1  0.598  0.000  0.250  1.0
  O  O22  1  0.667  0.333  0.843  1.0
  O  O23  1  0.333  0.667  0.157  1.0
  O  O24  1  0.333  0.667  0.343  1.0
  O  O25  1  0.333  0.667  0.657  1.0
  O  O26  1  0.667  0.333  0.657  1.0
  O  O27  1  0.667  0.333  0.343  1.0
  O  O28  1  0.667  0.333  0.157  1.0
  O  O29  1  0.333  0.667  0.843  1.0
  O  O30  1  0.768  0.768  0.343  1.0
  O  O31  1  0.232  0.232  0.657  1.0
  O  O32  1  0.000  0.232  0.343  1.0
  O  O33  1  0.232  0.232  0.843  1.0
  O  O34  1  0.000  0.232  0.157  1.0
  O  O35  1  0.000  0.768  0.657  1.0
  O  O36  1  0.768  0.768  0.157  1.0
  O  O37  1  0.000  0.768  0.843  1.0
  O  O38  1  0.232  0.000  0.343  1.0
  O  O39  1  0.768  0.000  0.657  1.0
  O  O40  1  0.768  0.000  0.843  1.0
  O  O41  1  0.232  0.000  0.157  1.0
  O  O42  1  0.596  0.596  0.936  1.0
  O  O43  1  0.404  0.404  0.064  1.0
  O  O44  1  0.000  0.404  0.936  1.0
  O  O45  1  0.404  0.404  0.436  1.0
  O  O46  1  0.000  0.404  0.564  1.0
  O  O47  1  0.000  0.596  0.064  1.0
  O  O48  1  0.596  0.596  0.564  1.0
  O  O49  1  0.000  0.596  0.436  1.0
  O  O50  1  0.404  0.000  0.936  1.0
  O  O51  1  0.596  0.000  0.064  1.0
  O  O52  1  0.596  0.000  0.436  1.0
  O  O53  1  0.404  0.000  0.564  1.0
[/CIF]
.