data_ZnPbSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.09
_cell_length_b   5.09
_cell_length_c   5.09
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   ZnPbSe2
_chemical_formula_sum   'Zn1 Pb1 Se2'
_cell_volume   93.28
_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
  Zn  Zn3  1  0.0  0.0  0.0  1.0
  Pb  Pb0  1  0.6  0.6  0.6  1.0
  Se  Se1  1  0.4  0.4  0.4  1.0
  Se  Se2  1  0.8  0.8  0.8  1.0

data_ZnPbSe2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.09
_cell_length_b   5.09
_cell_length_c   12.47
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   ZnPbSe2
_chemical_formula_sum   'Zn3 Pb3 Se6'
_cell_volume   279.83
_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
  Zn  Zn0  3  0.0  0.0  0.0  1.0
  Pb  Pb1  3  0.0  0.0  0.4  1.0
  Se  Se2  3  0.0  0.0  0.2  1.0
  Se  Se3  3  0.0  0.0  0.6  1.0

Zn Pb Se Se
Zn Pb Se Se 0 3 - - - 0 3 - - o 0 3 o - - 0 3 - o - 0 1 - - o 0 1 - o - 0 1 o - - 0 2 - o o 0 2 o - o 0 2 o o - 1 2 o o o 1 2 o + o 1 2 + o o 1 2 o o + 1 3 o o o 2 3 - o o 2 3 o - o 2 3 o o - 
ZnPbSe2 crystallizes in the trigonal R3m space group. Zn(1) is bonded in a distorted single-bond geometry to three equivalent Pb(1), one Se(2), and three equivalent Se(1) atoms. All Zn(1)-Pb(1) bond lengths are 3.06 Å. The Zn(1)-Se(2) bond length is 2.50 Å. All Zn(1)-Se(1) bond lengths are 3.05 Å. Pb(1) is bonded in a 5-coordinate geometry to three equivalent Zn(1), one Se(1), and one Se(2) atom. The Pb(1)-Se(1) bond length is 2.50 Å. The Pb(1)-Se(2) bond length is 2.50 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Zn(1) and one Pb(1) atom to form distorted corner-sharing SeZn3Pb tetrahedra. In the second Se site, Se(2) is bonded in a linear geometry to one Zn(1) and one Pb(1) atom.