data_Mg2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.98
_cell_length_b   5.04
_cell_length_c   7.74
_cell_angle_alpha   92.62
_cell_angle_beta   100.95
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2Si
_chemical_formula_sum   'Mg4 Si2'
_cell_volume   113.87
_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
  Mg  Mg0  1  0.49  0.59  0.1  1.0
  Mg  Mg1  1  0.51  0.24  0.86  1.0
  Mg  Mg2  1  0.01  0.09  0.49  1.0
  Mg  Mg3  1  0.99  0.44  0.73  1.0
  Si  Si4  1  0.49  0.95  0.9  1.0
  Si  Si5  1  0.02  0.73  0.69  1.0

data_Mg2Si
_symmetry_space_group_name_H-M   P-1
_cell_length_a   2.98
_cell_length_b   5.04
_cell_length_c   7.74
_cell_angle_alpha   92.62
_cell_angle_beta   100.95
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   2
_chemical_formula_structural   Mg2Si
_chemical_formula_sum   'Mg4 Si2'
_cell_volume   113.87
_cell_formula_units_Z   2
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
  Mg  Mg0  2  0.24  0.25  0.81  1.0
  Mg  Mg1  2  0.26  0.9  0.57  1.0
  Si  Si2  2  0.23  0.61  0.61  1.0

Mg Mg Mg Mg Si Si