data_Ga2Cu2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.73
_cell_length_b   6.73
_cell_length_c   6.73
_cell_angle_alpha   148.46
_cell_angle_beta   148.46
_cell_angle_gamma   45.21
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ga2Cu2Se
_chemical_formula_sum   'Ga2 Cu2 Se1'
_cell_volume   82.99
_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
  Ga  Ga2  1  0.0  0.0  0.5  1.0
  Ga  Ga3  1  0.0  0.0  0.92  1.0
  Cu  Cu0  1  0.0  0.83  0.1  1.0
  Cu  Cu1  1  0.83  0.0  0.1  1.0
  Se  Se4  1  0.0  0.0  0.0  1.0

data_Ga2Cu2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.17
_cell_length_b   5.17
_cell_length_c   6.73
_cell_angle_alpha   90.0
_cell_angle_beta   112.61
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Ga2Cu2Se
_chemical_formula_sum   'Ga4 Cu4 Se2'
_cell_volume   165.99
_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
  Ga  Ga0  2  0.0  0.0  0.08  1.0
  Ga  Ga1  2  0.0  0.0  0.5  1.0
  Cu  Cu2  4  0.41  0.41  0.72  1.0
  Se  Se3  2  0.0  0.0  0.0  1.0

Ga Ga Cu Cu Se
Cu2Ga2Se crystallizes in the monoclinic Cm space group. Cu(1) is bonded in a 3-coordinate geometry to one Cu(1), two equivalent Ga(1), and one Se(1) atom. The Cu(1)-Cu(1) bond length is 0.89 Å. There is one shorter (1.76 Å) and one longer (2.99 Å) Cu(1)-Ga(1) bond length. The Cu(1)-Se(1) bond length is 1.79 Å. There are two inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 5-coordinate geometry to four equivalent Cu(1) and one Ga(2) atom. The Ga(1)-Ga(2) bond length is 2.86 Å. In the second Ga site, Ga(2) is bonded in a single-bond geometry to one Ga(1) and one Se(1) atom. The Ga(2)-Se(1) bond length is 0.53 Å. Se(1) is bonded in a distorted single-bond geometry to two equivalent Cu(1) and one Ga(2) atom.