data_[Mg3Fe6Si3O18]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Mg  1.3100  1.5000  0.8600
  Fe  1.8300  1.4000  0.8525
  Si  1.9000  1.1000  0.5400
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [R3]
_cell_length_a [4.9284]
_cell_length_b [4.9284]
_cell_length_c [13.5416]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [146]
_chemical_formula_structural [MgFe2SiO6]
_chemical_formula_sum '[Mg3 Fe6 Si3 O18]'
_cell_volume [284.8434]
_cell_formula_units_Z [3]
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  3  0.0000  0.0000  0.8069  1
  Fe  Fe1  3  0.0000  0.0000  0.0099  1
  Fe  Fe2  3  0.0000  0.0000  0.5264  1
  Si  Si3  3  0.0000  0.0000  0.3253  1
  O  O4  9  0.0358  0.3389  0.9226  1
  O  O5  9  0.0504  0.6778  0.0761  1
]