data_CuSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.58
_cell_length_b   3.58
_cell_length_c   7.09
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CuSe
_chemical_formula_sum   'Cu2 Se2'
_cell_volume   78.57
_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
  Cu  Cu0  1  0.79  0.03  0.37  1.0
  Cu  Cu1  1  0.0  0.06  0.72  1.0
  Se  Se2  1  0.79  0.03  0.88  1.0
  Se  Se3  1  0.0  0.06  0.21  1.0

data_CuSe
_symmetry_space_group_name_H-M   P-1
_cell_length_a   3.58
_cell_length_b   3.58
_cell_length_c   7.09
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   2
_chemical_formula_structural   CuSe
_chemical_formula_sum   'Cu2 Se2'
_cell_volume   78.57
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-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
  Cu  Cu0  2  0.39  0.98  0.33  1.0
  Se  Se1  2  0.39  0.98  0.83  1.0

Cu Cu Se Se
Cu Cu Se Se 0 3 + o o 1 2 - o o 
CuSe is Hg_xSn structured and crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two selanylidenecopper molecules. Cu(1) is bonded in a single-bond geometry to one Se(1) atom. The Cu(1)-Se(1) bond length is 1.34 Å. Se(1) is bonded in a single-bond geometry to one Cu(1) atom.