data_HgSb2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.2
_cell_length_b   5.2
_cell_length_c   5.2
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HgSb2Se
_chemical_formula_sum   'Hg1 Sb2 Se1'
_cell_volume   99.63
_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  Hg0  1  0.68  0.68  0.68  1.0
  Sb  Sb1  1  0.84  0.84  0.84  1.0
  Sb  Sb2  1  0.52  0.52  0.52  1.0
  Se  Se3  1  0.0  0.0  0.0  1.0

data_HgSb2Se
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.2
_cell_length_b   5.2
_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   HgSb2Se
_chemical_formula_sum   'Hg3 Sb6 Se3'
_cell_volume   298.88
_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  0.32  1.0
  Sb  Sb1  3  0.0  0.0  0.16  1.0
  Sb  Sb2  3  0.0  0.0  0.48  1.0
  Se  Se3  3  0.0  0.0  0.0  1.0

Hg Sb Sb Se
Hg Sb Sb Se 0 2 o o o 0 1 o o o 1 3 + + + 
HgSb2Se crystallizes in the trigonal R3m space group. Hg(1) is bonded to one Sb(1), one Sb(2), and three equivalent Se(1) atoms to form HgSb2Se3 trigonal bipyramids that share corners with six equivalent Hg(1)Sb2Se3 trigonal bipyramids and  a cornercorner with one Se(1)Hg3Sb trigonal pyramid. The Hg(1)-Sb(1) bond length is 2.04 Å. The Hg(1)-Sb(2) bond length is 2.04 Å. All Hg(1)-Se(1) bond lengths are 3.01 Å. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a distorted linear geometry to one Hg(1) and one Se(1) atom. The Sb(1)-Se(1) bond length is 2.04 Å. In the second Sb site, Sb(2) is bonded in a distorted single-bond geometry to one Hg(1) atom. Se(1) is bonded to three equivalent Hg(1) and one Sb(1) atom to form distorted SeHg3Sb trigonal pyramids that share  a cornercorner with one Hg(1)Sb2Se3 trigonal bipyramid and corners with six equivalent Se(1)Hg3Sb trigonal pyramids.