data_Mg3Si2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.42
_cell_length_b   5.42
_cell_length_c   15.01
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   59.83
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg3Si2O9
_chemical_formula_sum   'Mg6 Si4 O18'
_cell_volume   380.98
_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  0.7  0.73  0.91  1.0
  Mg  Mg1  1  0.7  0.27  0.41  1.0
  Mg  Mg2  1  0.72  0.54  0.88  1.0
  Mg  Mg3  1  0.67  0.54  0.88  1.0
  Mg  Mg4  1  0.67  0.46  0.38  1.0
  Mg  Mg5  1  0.72  0.46  0.38  1.0
  Si  Si6  1  0.13  0.53  0.07  1.0
  Si  Si7  1  0.26  0.53  0.07  1.0
  Si  Si8  1  0.26  0.47  0.56  1.0
  Si  Si9  1  0.13  0.47  0.56  1.0
  O  O10  1  0.7  0.52  0.56  1.0
  O  O11  1  0.7  0.48  0.06  1.0
  O  O12  1  0.33  0.18  0.54  1.0
  O  O13  1  0.06  0.18  0.54  1.0
  O  O14  1  0.06  0.82  0.03  1.0
  O  O15  1  0.33  0.82  0.03  1.0
  O  O16  1  0.13  0.52  0.72  1.0
  O  O17  1  0.27  0.52  0.72  1.0
  O  O18  1  0.27  0.48  0.21  1.0
  O  O19  1  0.13  0.48  0.21  1.0
  O  O20  1  0.7  0.81  0.13  1.0
  O  O21  1  0.7  0.19  0.62  1.0
  O  O22  1  0.7  0.57  0.8  1.0
  O  O23  1  0.7  0.43  0.3  1.0
  O  O24  1  0.25  0.63  0.8  1.0
  O  O25  1  0.14  0.63  0.8  1.0
  O  O26  1  0.14  0.37  0.3  1.0
  O  O27  1  0.25  0.37  0.3  1.0

data_Mg3Si2O9
_symmetry_space_group_name_H-M   P2_1
_cell_length_a   5.41
_cell_length_b   15.01
_cell_length_c   5.42
_cell_angle_alpha   90.0
_cell_angle_beta   119.92
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   4
_chemical_formula_structural   Mg3Si2O9
_chemical_formula_sum   'Mg6 Si4 O18'
_cell_volume   380.98
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-x, 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
  Mg  Mg0  2  0.27  0.91  0.27  1.0
  Mg  Mg1  2  0.46  0.88  0.44  1.0
  Mg  Mg2  2  0.46  0.88  0.48  1.0
  Si  Si3  2  0.47  0.07  0.04  1.0
  Si  Si4  2  0.47  0.07  0.91  1.0
  O  O5  2  0.18  0.04  0.55  1.0
  O  O6  2  0.18  0.04  0.82  1.0
  O  O7  2  0.19  0.13  0.19  1.0
  O  O8  2  0.37  0.8  0.82  1.0
  O  O9  2  0.37  0.8  0.93  1.0
  O  O10  2  0.43  0.8  0.43  1.0
  O  O11  2  0.48  0.72  0.05  1.0
  O  O12  2  0.48  0.72  0.91  1.0
  O  O13  2  0.48  0.56  0.48  1.0

Mg Mg Mg Mg Mg Mg Si Si Si Si O O O O O O O O O O O O O O O O O O