data_MgNb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.91
_cell_length_b   2.91
_cell_length_c   9.72
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   107.39
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgNb
_chemical_formula_sum   'Mg2 Nb2'
_cell_volume   78.44
_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  0.72  0.83  0.55  1.0
  Mg  Mg1  1  0.72  0.17  0.17  1.0
  Nb  Nb2  1  0.72  0.83  0.63  1.0
  Nb  Nb3  1  0.72  0.17  0.09  1.0

data_MgNb
_symmetry_space_group_name_H-M   P-1
_cell_length_a   2.91
_cell_length_b   2.91
_cell_length_c   9.72
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   107.39
_symmetry_Int_Tables_number   2
_chemical_formula_structural   MgNb
_chemical_formula_sum   'Mg2 Nb2'
_cell_volume   78.44
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-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  2  0.5  0.17  0.81  1.0
  Nb  Nb1  2  0.5  0.17  0.73  1.0

Mg Mg Nb Nb
Mg Mg Nb Nb 0 2 o o o 1 3 o o o 