data_MgSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.88
_cell_length_b   5.88
_cell_length_c   5.88
_cell_angle_alpha   144.46
_cell_angle_beta   139.32
_cell_angle_gamma   55.11
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgSi
_chemical_formula_sum   'Mg2 Si2'
_cell_volume   76.53
_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  0.79  0.98  0.05  1.0
  Mg  Mg1  1  0.0  0.07  0.17  1.0
  Si  Si2  1  0.0  0.02  0.44  1.0
  Si  Si3  1  0.79  0.02  0.78  1.0

data_MgSi
_symmetry_space_group_name_H-M   P-1
_cell_length_a   3.59
_cell_length_b   4.09
_cell_length_c   5.88
_cell_angle_alpha   110.34
_cell_angle_beta   107.77
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   2
_chemical_formula_structural   MgSi
_chemical_formula_sum   'Mg2 Si2'
_cell_volume   76.53
_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  0.46  0.52  0.41  1.0
  Si  Si1  2  0.27  0.17  0.27  1.0

Mg Mg Si Si