data_Si2NiSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.89
_cell_length_b   6.89
_cell_length_c   6.45
_cell_angle_alpha   110.73
_cell_angle_beta   110.73
_cell_angle_gamma   29.26
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si2NiSe4
_chemical_formula_sum   'Si2 Ni1 Se4'
_cell_volume   139.2
_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  Si0  1  0.81  0.0  0.68  1.0
  Si  Si1  1  0.16  0.0  0.32  1.0
  Ni  Ni2  1  0.0  0.0  0.0  1.0
  Se  Se3  1  0.59  0.0  0.85  1.0
  Se  Se4  1  0.38  0.0  0.16  1.0
  Se  Se5  1  1.0  0.0  0.07  1.0
  Se  Se6  1  0.97  0.0  0.93  1.0

data_Si2NiSe4
_symmetry_space_group_name_H-M   P1
_cell_length_a   3.48
_cell_length_b   6.45
_cell_length_c   6.89
_cell_angle_alpha   110.73
_cell_angle_beta   104.63
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si2NiSe4
_chemical_formula_sum   'Si2 Ni1 Se4'
_cell_volume   139.2
_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  Si0  1  0.0  0.32  0.16  1.0
  Si  Si1  1  0.0  0.68  0.81  1.0
  Ni  Ni2  1  0.0  0.0  0.0  1.0
  Se  Se3  1  0.0  0.07  1.0  1.0
  Se  Se4  1  0.0  0.16  0.38  1.0
  Se  Se5  1  0.0  0.85  0.59  1.0
  Se  Se6  1  0.0  0.93  0.97  1.0

Si Si Ni Se Se Se Se