data_Mg2CuSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.72
_cell_length_b   5.72
_cell_length_c   5.72
_cell_angle_alpha   127.77
_cell_angle_beta   122.68
_cell_angle_gamma   81.24
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2CuSe2
_chemical_formula_sum   'Mg2 Cu1 Se2'
_cell_volume   119.83
_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  Mg1  1  0.0  0.74  0.81  1.0
  Mg  Mg2  1  0.52  0.0  0.53  1.0
  Cu  Cu0  1  0.0  0.0  0.0  1.0
  Se  Se3  1  0.0  0.0  0.33  1.0
  Se  Se4  1  0.0  0.0  0.35  1.0

data_Mg2CuSe2
_symmetry_space_group_name_H-M   P1
_cell_length_a   5.03
_cell_length_b   5.48
_cell_length_c   5.72
_cell_angle_alpha   118.66
_cell_angle_beta   116.12
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2CuSe2
_chemical_formula_sum   'Mg2 Cu1 Se2'
_cell_volume   119.83
_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  Mg0  1  0.19  0.93  0.93  1.0
  Mg  Mg1  1  0.99  0.47  0.99  1.0
  Cu  Cu2  1  0.0  0.0  0.0  1.0
  Se  Se3  1  0.65  0.65  0.65  1.0
  Se  Se4  1  0.67  0.67  0.67  1.0

Mg Mg Cu Se Se