data_HgAs2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.89
_cell_length_b   3.89
_cell_length_c   5.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HgAs2Se
_chemical_formula_sum   'Hg1 As2 Se1'
_cell_volume   89.84
_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  Hg2  1  0.94  0.94  0.0  1.0
  As  As0  1  0.0  0.94  0.97  1.0
  As  As1  1  0.94  0.0  0.97  1.0
  Se  Se3  1  0.0  0.0  0.0  1.0

data_HgAs2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.5
_cell_length_b   5.5
_cell_length_c   5.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   HgAs2Se
_chemical_formula_sum   'Hg2 As4 Se2'
_cell_volume   179.69
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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  2  0.44  0.5  -0.0  1.0
  As  As1  4  0.47  0.47  0.97  1.0
  Se  Se2  2  0.0  0.0  0.0  1.0

Hg As As Se
HgAs2Se is Indium-like structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two HgAs2Se clusters. Hg(1) is bonded in a 3-coordinate geometry to two equivalent As(1) and one Se(1) atom. Both Hg(1)-As(1) bond lengths are 0.28 Å. The Hg(1)-Se(1) bond length is 0.30 Å. As(1) is bonded in a 2-coordinate geometry to one Hg(1) and one Se(1) atom. The As(1)-Se(1) bond length is 0.28 Å. Se(1) is bonded in a 3-coordinate geometry to one Hg(1) and two equivalent As(1) atoms.