data_Mg2Cu4Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.37
_cell_length_b   5.37
_cell_length_c   5.37
_cell_angle_alpha   111.53
_cell_angle_beta   111.53
_cell_angle_gamma   105.43
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2Cu4Se
_chemical_formula_sum   'Mg2 Cu4 Se1'
_cell_volume   118.61
_cell_formula_units_Z   1
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  Mg4  1  0.02  0.0  0.63  1.0
  Mg  Mg5  1  0.0  0.02  0.63  1.0
  Cu  Cu0  1  0.78  0.22  0.25  1.0
  Cu  Cu1  1  0.22  0.78  0.25  1.0
  Cu  Cu2  1  0.22  0.22  0.25  1.0
  Cu  Cu3  1  0.8  0.8  0.0  1.0
  Se  Se6  1  0.0  0.0  0.0  1.0

data_Mg2Cu4Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.5
_cell_length_b   8.54
_cell_length_c   5.37
_cell_angle_alpha   90.0
_cell_angle_beta   127.28
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Mg2Cu4Se
_chemical_formula_sum   'Mg4 Cu8 Se2'
_cell_volume   237.22
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -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  4  0.38  0.01  0.37  1.0
  Cu  Cu1  4  0.25  0.28  0.75  1.0
  Cu  Cu2  2  0.3  0.5  0.0  1.0
  Cu  Cu3  2  0.47  0.5  0.75  1.0
  Se  Se4  2  0.0  0.0  0.0  1.0

Mg Mg Cu Cu Cu Cu Se
Mg Mg Cu Cu Cu Cu Se 0 1 o o o 0 2 - o o 0 3 o - o 1 2 - o o 1 3 o - o 2 6 + o o 2 5 o - o 2 4 + o o 3 6 o + o 3 4 o + o 3 5 - o o 4 6 o o o 5 6 + + o 