data_Si3Ni
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.45
_cell_length_b   4.45
_cell_length_c   4.45
_cell_angle_alpha   129.15
_cell_angle_beta   129.15
_cell_angle_gamma   74.77
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si3Ni
_chemical_formula_sum   'Si3 Ni1'
_cell_volume   51.5
_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  Si1  1  0.0  0.91  0.77  1.0
  Si  Si2  1  0.0  0.0  0.0  1.0
  Si  Si3  1  0.91  0.0  0.77  1.0
  Ni  Ni0  1  0.0  0.0  0.53  1.0

data_Si3Ni
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.4
_cell_length_b   5.4
_cell_length_c   4.45
_cell_angle_alpha   90.0
_cell_angle_beta   127.38
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Si3Ni
_chemical_formula_sum   'Si6 Ni2'
_cell_volume   103.0
_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
  Si  Si0  4  0.19  0.05  0.14  1.0
  Si  Si1  2  0.0  0.0  0.0  1.0
  Ni  Ni2  2  0.47  0.0  0.47  1.0

Si Si Si Ni
Si Si Si Ni 0 2 - + o 0 1 o + + 0 3 o + o 1 2 - o - 2 3 + o o 