data_MgHg4Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.05
_cell_length_b   6.05
_cell_length_c   6.05
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgHg4Se
_chemical_formula_sum   'Mg1 Hg4 Se1'
_cell_volume   156.65
_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
  Mg  Mg4  1  0.0  0.0  0.0  1.0
  Hg  Hg0  1  0.21  0.21  0.35  1.0
  Hg  Hg1  1  0.21  0.35  0.21  1.0
  Hg  Hg2  1  0.35  0.21  0.21  1.0
  Hg  Hg3  1  0.35  0.35  0.35  1.0
  Se  Se5  1  0.14  0.14  0.14  1.0

data_MgHg4Se
_symmetry_space_group_name_H-M   R3m
_cell_length_a   6.05
_cell_length_b   6.05
_cell_length_c   14.82
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   MgHg4Se
_chemical_formula_sum   'Mg3 Hg12 Se3'
_cell_volume   469.95
_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
  Mg  Mg0  3  0.0  0.0  0.0  1.0
  Hg  Hg1  9  0.05  0.09  0.74  1.0
  Hg  Hg2  3  0.0  0.0  0.65  1.0
  Se  Se3  3  0.0  0.0  0.86  1.0

Mg Hg Hg Hg Hg Se
Mg Hg Hg Hg Hg Se 0 5 o o o 1 3 o o o 1 2 o o o 1 4 o o o 1 5 o o o 2 3 o o o 2 4 o o o 2 5 o o o 3 4 o o o 3 5 o o o 
MgHg4Se crystallizes in the trigonal R3m space group. Mg(1) is bonded in a distorted single-bond geometry to three equivalent Hg(1) and one Se(1) atom. All Mg(1)-Hg(1) bond lengths are 3.23 Å. The Mg(1)-Se(1) bond length is 2.06 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 5-coordinate geometry to one Mg(1), one Hg(2), two equivalent Hg(1), and one Se(1) atom. The Hg(1)-Hg(2) bond length is 1.42 Å. Both Hg(1)-Hg(1) bond lengths are 0.82 Å. The Hg(1)-Se(1) bond length is 1.79 Å. In the second Hg site, Hg(2) is bonded in a 3-coordinate geometry to three equivalent Hg(1) atoms. Se(1) is bonded in a distorted single-bond geometry to one Mg(1) and three equivalent Hg(1) atoms.