data_Cs3TlSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.89
_cell_length_b   6.89
_cell_length_c   6.89
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Cs3TlSe
_chemical_formula_sum   'Cs3 Tl1 Se1'
_cell_volume   326.91
_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
  Cs  Cs0  1  0.44  0.0  0.44  1.0
  Cs  Cs1  1  0.44  0.44  0.0  1.0
  Cs  Cs2  1  0.0  0.44  0.44  1.0
  Tl  Tl3  1  0.44  0.44  0.44  1.0
  Se  Se4  1  0.0  0.0  0.0  1.0

data_Cs3TlSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   9.74
_cell_length_b   9.74
_cell_length_c   11.93
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Cs3TlSe
_chemical_formula_sum   'Cs9 Tl3 Se3'
_cell_volume   980.73
_cell_formula_units_Z   3
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  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  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'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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
  Cs  Cs0  9  0.04  0.52  0.96  1.0
  Tl  Tl1  3  0.0  0.0  0.44  1.0
  Se  Se2  3  0.0  0.0  0.0  1.0

Cs Cs Cs Tl Se
Cs3TlSe crystallizes in the trigonal R3m space group. Cs(1) is bonded in a 3-coordinate geometry to two equivalent Tl(1) and one Se(1) atom. There is one shorter (3.06 Å) and one longer (3.83 Å) Cs(1)-Tl(1) bond length. The Cs(1)-Se(1) bond length is 4.33 Å. Tl(1) is bonded to six equivalent Cs(1) atoms to form corner-sharing TlCs6 octahedra. The corner-sharing octahedra are not tilted. Se(1) is bonded in a 3-coordinate geometry to three equivalent Cs(1) atoms.