data_Si2As
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   18.64
_cell_length_b   18.64
_cell_length_c   18.64
_cell_angle_alpha   169.63
_cell_angle_beta   169.63
_cell_angle_gamma   14.69
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si2As
_chemical_formula_sum   'Si8 As4'
_cell_volume   209.93
_cell_formula_units_Z   4
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  Si4  1  0.0  0.68  0.46  1.0
  Si  Si5  1  0.0  0.68  0.03  1.0
  Si  Si6  1  0.0  0.0  0.19  1.0
  Si  Si7  1  0.0  0.0  0.79  1.0
  Si  Si8  1  0.68  0.0  0.92  1.0
  Si  Si9  1  0.68  0.0  0.57  1.0
  Si  Si10  1  0.0  0.0  0.16  1.0
  Si  Si11  1  0.0  0.0  0.81  1.0
  As  As0  1  0.0  0.68  0.7  1.0
  As  As1  1  0.0  0.68  0.79  1.0
  As  As2  1  0.0  0.0  0.43  1.0
  As  As3  1  0.0  0.0  0.54  1.0

data_Si2As
_symmetry_space_group_name_H-M   P1
_cell_length_a   3.37
_cell_length_b   3.37
_cell_length_c   18.64
_cell_angle_alpha   95.19
_cell_angle_beta   95.19
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si2As
_chemical_formula_sum   'Si8 As4'
_cell_volume   209.93
_cell_formula_units_Z   4
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  0.08  0.0  0.77  1.0
  Si  Si1  1  0.19  0.0  0.19  1.0
  Si  Si2  1  0.21  0.0  0.21  1.0
  Si  Si3  1  0.23  0.68  0.23  1.0
  Si  Si4  1  0.43  0.0  0.11  1.0
  Si  Si5  1  0.65  0.68  0.65  1.0
  Si  Si6  1  0.81  0.0  0.81  1.0
  Si  Si7  1  0.84  0.0  0.84  1.0
  As  As8  1  0.46  0.0  0.46  1.0
  As  As9  1  0.57  0.0  0.57  1.0
  As  As10  1  0.9  0.68  0.9  1.0
  As  As11  1  0.99  0.68  0.99  1.0

Si Si Si Si Si Si Si Si As As As As