data_Tb3Se4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.53
_cell_length_b   7.53
_cell_length_c   7.53
_cell_angle_alpha   109.47
_cell_angle_beta   109.47
_cell_angle_gamma   109.47
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Tb3Se4
_chemical_formula_sum   'Tb6 Se8'
_cell_volume   328.72
_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
  Tb  Tb8  1  0.83  0.26  0.35  1.0
  Tb  Tb9  1  0.35  0.83  0.26  1.0
  Tb  Tb10  1  0.17  0.09  0.35  1.0
  Tb  Tb11  1  0.09  0.35  0.17  1.0
  Tb  Tb12  1  0.35  0.17  0.09  1.0
  Tb  Tb13  1  0.26  0.35  0.83  1.0
  Se  Se0  1  0.54  0.46  0.81  1.0
  Se  Se1  1  0.37  0.63  0.98  1.0
  Se  Se2  1  0.46  0.81  0.54  1.0
  Se  Se3  1  0.54  0.54  0.54  1.0
  Se  Se4  1  0.98  0.37  0.63  1.0
  Se  Se5  1  0.81  0.54  0.46  1.0
  Se  Se6  1  0.63  0.98  0.37  1.0
  Se  Se7  1  0.72  0.72  0.72  1.0

data_Tb3Se4
_symmetry_space_group_name_H-M   R3
_cell_length_a   12.3
_cell_length_b   12.3
_cell_length_c   7.53
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   146
_chemical_formula_structural   Tb3Se4
_chemical_formula_sum   'Tb18 Se24'
_cell_volume   986.17
_cell_formula_units_Z   6
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  'x+2/3, y+1/3, z+1/3'
  5  '-y+2/3, x-y+1/3, z+1/3'
  6  '-x+y+2/3, -x+1/3, z+1/3'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
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
  Tb  Tb0  9  0.01  0.46  0.81  1.0
  Tb  Tb1  9  0.14  0.12  0.2  1.0
  Se  Se2  9  0.04  0.35  0.33  1.0
  Se  Se3  9  0.19  0.73  0.27  1.0
  Se  Se4  3  0.0  0.0  0.54  1.0
  Se  Se5  3  0.0  0.0  0.72  1.0

Tb Tb Tb Tb Tb Tb Se Se Se Se Se Se Se Se
Tb3Se4 crystallizes in the trigonal R3 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 3-coordinate geometry to one Se(1) and two equivalent Se(2) atoms. The Tb(1)-Se(1) bond length is 2.08 Å. There is one shorter (1.77 Å) and one longer (2.23 Å) Tb(1)-Se(2) bond length. In the second Tb site, Tb(2) is bonded in a 2-coordinate geometry to one Se(1) and one Se(3) atom. The Tb(2)-Se(1) bond length is 3.07 Å. The Tb(2)-Se(3) bond length is 3.03 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted single-bond geometry to one Tb(1) and one Tb(2) atom. In the second Se site, Se(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Tb(1) atoms. In the third Se site, Se(3) is bonded in a distorted single-bond geometry to three equivalent Tb(2) and one Se(4) atom. The Se(3)-Se(4) bond length is 1.31 Å. In the fourth Se site, Se(4) is bonded in a single-bond geometry to one Se(3) atom.