data_NbHg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.91
_cell_length_b   2.91
_cell_length_c   9.34
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NbHg
_chemical_formula_sum   'Nb2 Hg2'
_cell_volume   79.23
_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
  Nb  Nb2  1  0.46  0.0  0.12  1.0
  Nb  Nb3  1  0.0  0.46  0.22  1.0
  Hg  Hg0  1  0.46  0.0  0.93  1.0
  Hg  Hg1  1  0.0  0.46  0.41  1.0

data_NbHg
_symmetry_space_group_name_H-M   C2/m
_cell_length_a   4.12
_cell_length_b   4.12
_cell_length_c   9.34
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   12
_chemical_formula_structural   NbHg
_chemical_formula_sum   'Nb4 Hg4'
_cell_volume   158.47
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-x, -y, -z'
  3  '-x, y, -z'
  4  'x, -y, z'
  5  'x+1/2, y+1/2, z'
  6  '-x+1/2, -y+1/2, -z'
  7  '-x+1/2, y+1/2, -z'
  8  '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
  Nb  Nb0  4  0.23  0.5  0.95  1.0
  Hg  Hg1  4  0.23  0.5  0.76  1.0

Nb Nb Hg Hg
Nb Nb Hg Hg 0 1 o - o 0 1 o o o 0 1 + o o 0 2 o o - 1 3 o o o 