data_Hg2SeBr
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.21
_cell_length_b   5.21
_cell_length_c   5.21
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Hg2SeBr
_chemical_formula_sum   'Hg2 Se1 Br1'
_cell_volume   99.83
_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
  Hg  Hg1  1  0.84  0.84  0.84  1.0
  Hg  Hg2  1  0.68  0.68  0.68  1.0
  Se  Se3  1  0.0  0.0  0.0  1.0
  Br  Br0  1  0.52  0.52  0.52  1.0

data_Hg2SeBr
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.21
_cell_length_b   5.21
_cell_length_c   12.75
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Hg2SeBr
_chemical_formula_sum   'Hg6 Se3 Br3'
_cell_volume   299.49
_cell_formula_units_Z   3
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
  Hg  Hg0  3  0.0  0.0  0.16  1.0
  Hg  Hg1  3  0.0  0.0  0.32  1.0
  Se  Se2  3  0.0  0.0  0.0  1.0
  Br  Br3  3  0.0  0.0  0.48  1.0

Hg Hg Se Br
Hg2SeBr crystallizes in the trigonal R3m space group. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to one Hg(2), one Se(1), and three equivalent Br(1) atoms to form distorted HgHgSeBr3 trigonal bipyramids that share corners with six equivalent Hg(1)HgSeBr3 trigonal bipyramids,  a cornercorner with one Br(1)Hg4 trigonal pyramid, and corners with three equivalent Se(1)Hg4 trigonal pyramids. The Hg(1)-Hg(2) bond length is 2.03 Å. The Hg(1)-Se(1) bond length is 2.03 Å. All Hg(1)-Br(1) bond lengths are 3.01 Å. In the second Hg site, Hg(2) is bonded in a distorted single-bond geometry to one Hg(1), three equivalent Se(1), and one Br(1) atom. All Hg(2)-Se(1) bond lengths are 3.01 Å. The Hg(2)-Br(1) bond length is 2.03 Å. Se(1) is bonded to one Hg(1) and three equivalent Hg(2) atoms to form distorted SeHg4 trigonal pyramids that share corners with three equivalent Hg(1)HgSeBr3 trigonal bipyramids, corners with six equivalent Se(1)Hg4 trigonal pyramids, and edges with three equivalent Br(1)Hg4 trigonal pyramids. Br(1) is bonded to one Hg(2) and three equivalent Hg(1) atoms to form distorted BrHg4 trigonal pyramids that share  a cornercorner with one Hg(1)HgSeBr3 trigonal bipyramid, corners with six equivalent Br(1)Hg4 trigonal pyramids, and edges with three equivalent Se(1)Hg4 trigonal pyramids.