data_Mg2Cu2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.88
_cell_length_b   7.88
_cell_length_c   7.88
_cell_angle_alpha   154.7
_cell_angle_beta   154.7
_cell_angle_gamma   36.08
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2Cu2Se
_chemical_formula_sum   'Mg2 Cu2 Se1'
_cell_volume   89.27
_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  Mg2  1  0.0  0.0  0.92  1.0
  Mg  Mg3  1  0.0  0.0  0.06  1.0
  Cu  Cu0  1  0.0  0.73  0.75  1.0
  Cu  Cu1  1  0.73  0.0  0.75  1.0
  Se  Se4  1  0.0  0.0  0.0  1.0

data_Mg2Cu2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.88
_cell_length_b   4.88
_cell_length_c   7.88
_cell_angle_alpha   90.0
_cell_angle_beta   108.04
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Mg2Cu2Se
_chemical_formula_sum   'Mg4 Cu4 Se2'
_cell_volume   178.54
_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  2  0.06  0.0  0.06  1.0
  Mg  Mg1  2  0.42  0.5  0.92  1.0
  Cu  Cu2  4  0.38  0.36  0.02  1.0
  Se  Se3  2  0.0  0.0  0.0  1.0

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