data_Na2Br
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.38
_cell_length_b   6.38
_cell_length_c   6.38
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2Br
_chemical_formula_sum   'Na4 Br2'
_cell_volume   183.52
_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
  Na  Na2  1  0.38  0.38  0.64  1.0
  Na  Na3  1  0.64  0.38  0.38  1.0
  Na  Na4  1  0.38  0.64  0.38  1.0
  Na  Na5  1  0.64  0.64  0.64  1.0
  Br  Br0  1  0.0  0.0  0.0  1.0
  Br  Br1  1  0.26  0.26  0.26  1.0

data_Na2Br
_symmetry_space_group_name_H-M   R3m
_cell_length_a   6.38
_cell_length_b   6.38
_cell_length_c   15.62
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Na2Br
_chemical_formula_sum   'Na12 Br6'
_cell_volume   550.55
_cell_formula_units_Z   6
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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
  Na  Na0  9  0.09  0.17  0.53  1.0
  Na  Na1  3  0.0  0.0  0.36  1.0
  Br  Br2  3  0.0  0.0  0.0  1.0
  Br  Br3  3  0.0  0.0  0.74  1.0

Na Na Na Na Br Br
Na Na Na Na Br Br 0 2 o o o 0 1 o o o 0 3 o o o 0 4 o o + 0 5 o o + 0 5 o o o 1 2 o o o 1 3 o o o 1 4 + o o 1 5 + o o 1 5 o o o 2 3 o o o 2 4 o + o 2 5 o + o 2 5 o o o 3 4 + + o 3 4 + o + 3 4 o + + 3 5 + o o 3 5 o + o 3 5 o o + 4 5 - o o 4 5 o - o 4 5 o o - 4 5 o o o 
Na2Br crystallizes in the trigonal R3m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one Na(2), two equivalent Na(1), one Br(1), and two equivalent Br(2) atoms. The Na(1)-Na(2) bond length is 2.82 Å. Both Na(1)-Na(1) bond lengths are 1.63 Å. The Na(1)-Br(1) bond length is 3.46 Å. There is one shorter (3.33 Å) and one longer (3.45 Å) Na(1)-Br(2) bond length. In the second Na site, Na(2) is bonded in a 3-coordinate geometry to three equivalent Na(1) atoms. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded in a 3-coordinate geometry to three equivalent Na(1) atoms. In the second Br site, Br(2) is bonded in a 6-coordinate geometry to six equivalent Na(1) atoms.