data_Tl2NiSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.5
_cell_length_b   4.5
_cell_length_c   4.69
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Tl2NiSe
_chemical_formula_sum   'Tl2 Ni1 Se1'
_cell_volume   94.98
_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  Tl2  1  0.25  0.0  0.34  1.0
  Tl  Tl3  1  0.0  0.25  0.34  1.0
  Ni  Ni0  1  0.0  0.0  0.0  1.0
  Se  Se1  1  0.25  0.25  0.0  1.0

data_Tl2NiSe
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.36
_cell_length_b   6.36
_cell_length_c   4.69
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Tl2NiSe
_chemical_formula_sum   'Tl4 Ni2 Se2'
_cell_volume   189.95
_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
  Tl  Tl0  4  0.13  0.13  0.34  1.0
  Ni  Ni1  2  0.0  0.0  0.0  1.0
  Se  Se2  2  0.25  0.0  -0.0  1.0

Tl Tl Ni Se
Tl Tl Ni Se 0 2 o o o 0 1 o o o 0 3 o o o 1 2 o o o 1 3 o o o 2 3 o o o 
NiTl2Se is alpha Po structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two NiTl2Se clusters. Ni(1) is bonded in a distorted single-bond geometry to two equivalent Tl(1) and one Se(1) atom. Both Ni(1)-Tl(1) bond lengths are 1.97 Å. The Ni(1)-Se(1) bond length is 1.59 Å. Tl(1) is bonded in a 3-coordinate geometry to one Ni(1), one Tl(1), and one Se(1) atom. The Tl(1)-Tl(1) bond length is 1.59 Å. The Tl(1)-Se(1) bond length is 1.97 Å. Se(1) is bonded in a 3-coordinate geometry to one Ni(1) and two equivalent Tl(1) atoms.