data_TlAs4Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.1
_cell_length_b   6.1
_cell_length_c   6.1
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   TlAs4Se
_chemical_formula_sum   'Tl1 As4 Se1'
_cell_volume   160.24
_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
  Tl  Tl5  1  0.16  0.16  0.16  1.0
  As  As0  1  0.04  0.04  0.58  1.0
  As  As1  1  0.04  0.58  0.04  1.0
  As  As2  1  0.58  0.04  0.04  1.0
  As  As3  1  0.58  0.58  0.58  1.0
  Se  Se4  1  0.0  0.0  0.0  1.0

data_TlAs4Se
_symmetry_space_group_name_H-M   R3m
_cell_length_a   6.1
_cell_length_b   6.1
_cell_length_c   14.93
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   TlAs4Se
_chemical_formula_sum   'Tl3 As12 Se3'
_cell_volume   480.72
_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
  Tl  Tl0  3  0.0  0.0  0.84  1.0
  As  As1  9  0.18  0.36  0.78  1.0
  As  As2  3  0.0  0.0  0.42  1.0
  Se  Se3  3  0.0  0.0  0.0  1.0

Tl As As As As Se
TlAs4Se crystallizes in the trigonal R3m space group. Tl(1) is bonded in a tetrahedral geometry to three equivalent As(1) and one Se(1) atom. All Tl(1)-As(1) bond lengths are 2.15 Å. The Tl(1)-Se(1) bond length is 2.32 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded in a distorted bent 150 degrees geometry to one Tl(1), two equivalent As(2), and one Se(1) atom. Both As(1)-As(2) bond lengths are 3.08 Å. The As(1)-Se(1) bond length is 2.33 Å. In the second As site, As(2) is bonded in a hexagonal planar geometry to six equivalent As(1) atoms. Se(1) is bonded in a 4-coordinate geometry to one Tl(1) and three equivalent As(1) atoms.