data_PbSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.95
_cell_length_b   5.95
_cell_length_c   5.95
_cell_angle_alpha   55.06
_cell_angle_beta   55.06
_cell_angle_gamma   55.06
_symmetry_Int_Tables_number   1
_chemical_formula_structural   PbSe
_chemical_formula_sum   'Pb2 Se2'
_cell_volume   131.76
_cell_formula_units_Z   2
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
  Pb  Pb0  1  0.0  0.0  0.0  1.0
  Pb  Pb1  1  0.0  0.0  0.09  1.0
  Se  Se2  1  0.0  0.0  0.19  1.0
  Se  Se3  1  0.0  0.0  0.9  1.0

data_PbSe
_symmetry_space_group_name_H-M   C2/m
_cell_length_a   9.53
_cell_length_b   5.5
_cell_length_c   5.95
_cell_angle_alpha   90.0
_cell_angle_beta   122.26
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   12
_chemical_formula_structural   PbSe
_chemical_formula_sum   'Pb4 Se4'
_cell_volume   263.52
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-x, -y, -z'
  3  '-x, y, -z'
  4  'x, -y, z'
  5  'x+1/2, y+1/2, z'
  6  '-x+1/2, -y+1/2, -z'
  7  '-x+1/2, y+1/2, -z'
  8  '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
  Pb  Pb0  4  -0.0  0.0  0.04  1.0
  Se  Se1  4  0.0  0.0  0.15  1.0

Pb Pb Se Se