data_TaNb3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.31
_cell_length_b   3.31
_cell_length_c   6.62
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   TaNb3
_chemical_formula_sum   'Ta1 Nb3'
_cell_volume   72.51
_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
  Ta  Ta3  1  0.0  0.0  0.31  1.0
  Nb  Nb0  1  0.65  0.65  0.97  1.0
  Nb  Nb1  1  0.65  0.65  0.65  1.0
  Nb  Nb2  1  0.0  0.0  0.0  1.0

data_TaNb3
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.68
_cell_length_b   4.68
_cell_length_c   6.62
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   TaNb3
_chemical_formula_sum   'Ta2 Nb6'
_cell_volume   145.03
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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  2  0.0  0.0  0.31  1.0
  Nb  Nb1  2  0.0  0.0  0.0  1.0
  Nb  Nb2  2  0.15  0.5  0.65  1.0
  Nb  Nb3  2  0.15  0.5  0.97  1.0

Ta Nb Nb Nb
TaNb3 crystallizes in the monoclinic Cm space group. Ta(1) is bonded in a 1-coordinate geometry to one Nb(2) and one Nb(3) atom. The Ta(1)-Nb(2) bond length is 2.79 Å. The Ta(1)-Nb(3) bond length is 2.05 Å. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 4-coordinate geometry to one Nb(2) and three equivalent Nb(3) atoms. The Nb(1)-Nb(2) bond length is 2.06 Å. There is one shorter (1.63 Å) and two longer (2.46 Å) Nb(1)-Nb(3) bond lengths. In the second Nb site, Nb(2) is bonded in a 2-coordinate geometry to one Ta(1) and one Nb(1) atom. In the third Nb site, Nb(3) is bonded in a 2-coordinate geometry to one Ta(1) and three equivalent Nb(1) atoms.