data_TlSiSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.03
_cell_length_b   5.03
_cell_length_c   5.03
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   TlSiSe2
_chemical_formula_sum   'Tl1 Si1 Se2'
_cell_volume   90.09
_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  Tl3  1  0.34  0.34  0.34  1.0
  Si  Si2  1  0.0  0.0  0.0  1.0
  Se  Se0  1  0.56  0.56  0.56  1.0
  Se  Se1  1  0.78  0.78  0.78  1.0

data_TlSiSe2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.03
_cell_length_b   5.03
_cell_length_c   12.33
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   TlSiSe2
_chemical_formula_sum   'Tl3 Si3 Se6'
_cell_volume   270.27
_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  0.66  1.0
  Si  Si1  3  0.0  0.0  0.0  1.0
  Se  Se2  3  0.0  0.0  0.22  1.0
  Se  Se3  3  0.0  0.0  0.44  1.0

Tl Si Se Se
Tl Si Se Se 0 2 o - o 0 2 - o o 0 2 o o - 0 2 o o o 0 1 o o + 0 1 o + o 0 1 + o o 0 3 - o o 0 3 o - o 0 3 o o - 1 3 - - - 1 3 - - o 1 3 o - - 1 3 - o - 1 2 - - o 1 2 - o - 1 2 o - - 2 3 o - o 2 3 - o o 2 3 o o - 2 3 o o o 
TlSiSe2 crystallizes in the trigonal R3m space group. Tl(1) is bonded in a 10-coordinate geometry to three equivalent Si(1), three equivalent Se(2), and four equivalent Se(1) atoms. All Tl(1)-Si(1) bond lengths are 2.91 Å. All Tl(1)-Se(2) bond lengths are 3.20 Å. There is one shorter (2.72 Å) and three longer (3.22 Å) Tl(1)-Se(1) bond lengths. Si(1) is bonded to three equivalent Tl(1) and one Se(2) atom to form corner-sharing SiTl3Se trigonal pyramids. The Si(1)-Se(2) bond length is 2.72 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted single-bond geometry to four equivalent Tl(1) and one Se(2) atom. The Se(1)-Se(2) bond length is 2.72 Å. In the second Se site, Se(2) is bonded in a distorted single-bond geometry to three equivalent Tl(1), one Si(1), and one Se(1) atom.