data_Si2HgSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.74
_cell_length_b   3.98
_cell_length_c   5.63
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si2HgSe
_chemical_formula_sum   'Si2 Hg1 Se1'
_cell_volume   83.8
_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
  Si  Si2  1  0.87  0.0  0.82  1.0
  Si  Si3  1  0.0  0.0  0.0  1.0
  Hg  Hg0  1  0.0  0.99  0.82  1.0
  Se  Se1  1  0.87  0.99  0.0  1.0

data_Si2HgSe
_symmetry_space_group_name_H-M   Pm
_cell_length_a   3.74
_cell_length_b   3.98
_cell_length_c   5.63
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   6
_chemical_formula_structural   Si2HgSe
_chemical_formula_sum   'Si2 Hg1 Se1'
_cell_volume   83.8
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '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
  Si  Si0  1  0.0  0.5  0.0  1.0
  Si  Si1  1  0.87  0.5  0.82  1.0
  Hg  Hg2  1  -0.0  0.5  0.82  1.0
  Se  Se3  1  0.87  0.5  0.0  1.0

Si Si Hg Se
Si Si Hg Se 0 2 + - o 1 3 - - o 