data_Au3Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.38
_cell_length_b   5.38
_cell_length_c   5.38
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Au3Se
_chemical_formula_sum   'Au6 Se2'
_cell_volume   155.66
_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
  Au  Au0  1  0.34  0.0  0.69  1.0
  Au  Au1  1  0.03  0.0  0.69  1.0
  Au  Au2  1  0.69  0.34  0.0  1.0
  Au  Au3  1  0.69  0.03  0.0  1.0
  Au  Au4  1  0.0  0.69  0.03  1.0
  Au  Au5  1  0.0  0.69  0.34  1.0
  Se  Se6  1  0.69  0.69  0.69  1.0
  Se  Se7  1  0.0  0.0  0.0  1.0

data_Au3Se
_symmetry_space_group_name_H-M   R3
_cell_length_a   7.61
_cell_length_b   7.61
_cell_length_c   9.32
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   146
_chemical_formula_structural   Au3Se
_chemical_formula_sum   'Au18 Se6'
_cell_volume   466.97
_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
  Au  Au0  9  0.01  0.68  0.68  1.0
  Au  Au1  9  0.09  0.87  0.91  1.0
  Se  Se2  3  0.0  0.0  0.0  1.0
  Se  Se3  3  0.0  0.0  0.69  1.0

Au Au Au Au Au Au Se Se
Au3Se crystallizes in the trigonal R3 space group. There are two inequivalent Au sites. In the first Au site, Au(1) is bonded in a 1-coordinate geometry to one Au(2) and one Se(1) atom. The Au(1)-Au(2) bond length is 1.67 Å. The Au(1)-Se(1) bond length is 2.50 Å. In the second Au site, Au(2) is bonded in a 2-coordinate geometry to one Au(1), one Se(1), and one Se(2) atom. The Au(2)-Se(1) bond length is 2.50 Å. The Au(2)-Se(2) bond length is 1.68 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted hexagonal planar geometry to three equivalent Au(1) and three equivalent Au(2) atoms. In the second Se site, Se(2) is bonded in a 3-coordinate geometry to three equivalent Au(2) atoms.