data_SiHg3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.72
_cell_length_b   5.72
_cell_length_c   5.72
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   SiHg3
_chemical_formula_sum   'Si2 Hg6'
_cell_volume   187.39
_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
  Si  Si6  1  0.86  0.86  0.86  1.0
  Si  Si7  1  0.0  0.0  0.0  1.0
  Hg  Hg0  1  0.43  0.0  0.86  1.0
  Hg  Hg1  1  0.29  0.0  0.86  1.0
  Hg  Hg2  1  0.86  0.43  0.0  1.0
  Hg  Hg3  1  0.86  0.29  0.0  1.0
  Hg  Hg4  1  0.0  0.86  0.29  1.0
  Hg  Hg5  1  0.0  0.86  0.43  1.0

data_SiHg3
_symmetry_space_group_name_H-M   R3
_cell_length_a   8.09
_cell_length_b   8.09
_cell_length_c   9.91
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   146
_chemical_formula_structural   SiHg3
_chemical_formula_sum   'Si6 Hg18'
_cell_volume   562.16
_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  'x+1/3, y+2/3, z+2/3'
  5  '-y+1/3, x-y+2/3, z+2/3'
  6  '-x+y+1/3, -x+2/3, z+2/3'
  7  'x+2/3, y+1/3, z+1/3'
  8  '-y+2/3, x-y+1/3, z+1/3'
  9  '-x+y+2/3, -x+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
  Si  Si0  3  0.0  0.0  0.0  1.0
  Si  Si1  3  0.0  0.0  0.86  1.0
  Hg  Hg2  9  0.0  0.57  0.43  1.0
  Hg  Hg3  9  0.14  0.72  0.72  1.0

Si Si Hg Hg Hg Hg Hg Hg
Si Si Hg Hg Hg Hg Hg Hg 0 1 + + + 2 3 o o o 4 5 o o o 6 7 o o o 
Hg3Si crystallizes in the trigonal R3 space group. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 2-coordinate geometry to one Hg(2) and one Si(1) atom. The Hg(1)-Hg(2) bond length is 0.79 Å. The Hg(1)-Si(1) bond length is 2.59 Å. In the second Hg site, Hg(2) is bonded in a distorted bent 150 degrees geometry to one Hg(1) and one Si(2) atom. The Hg(2)-Si(2) bond length is 1.85 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a distorted tetrahedral geometry to three equivalent Hg(1) and one Si(2) atom. The Si(1)-Si(2) bond length is 1.38 Å. In the second Si site, Si(2) is bonded in a tetrahedral geometry to three equivalent Hg(2) and one Si(1) atom.