data_Cu2Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.85
_cell_length_b   4.85
_cell_length_c   7.78
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Cu2Si
_chemical_formula_sum   'Cu8 Si4'
_cell_volume   158.7
_cell_formula_units_Z   4
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  0.0  0.0  0.89  1.0
  Cu  Cu1  1  0.0  0.0  0.0  1.0
  Cu  Cu2  1  0.19  0.49  0.83  1.0
  Cu  Cu3  1  0.24  0.71  0.94  1.0
  Cu  Cu4  1  0.81  0.49  0.83  1.0
  Cu  Cu5  1  0.0  0.43  0.83  1.0
  Cu  Cu6  1  0.43  0.77  0.94  1.0
  Cu  Cu7  1  0.62  0.71  0.94  1.0
  Si  Si8  1  0.43  0.4  0.18  1.0
  Si  Si9  1  0.0  0.8  0.29  1.0
  Si  Si10  1  0.0  0.8  0.59  1.0
  Si  Si11  1  0.43  0.4  0.48  1.0

data_Cu2Si
_symmetry_space_group_name_H-M   P1
_cell_length_a   4.85
_cell_length_b   4.85
_cell_length_c   7.78
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Cu2Si
_chemical_formula_sum   'Cu8 Si4'
_cell_volume   158.7
_cell_formula_units_Z   4
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  0.0  0.0  0.0  1.0
  Cu  Cu1  1  0.0  0.0  0.89  1.0
  Cu  Cu2  1  0.0  0.43  0.83  1.0
  Si  Si3  1  0.0  0.8  0.29  1.0
  Si  Si4  1  0.0  0.8  0.59  1.0
  Cu  Cu5  1  0.19  0.49  0.83  1.0
  Cu  Cu6  1  0.24  0.71  0.94  1.0
  Si  Si7  1  0.43  0.4  0.18  1.0
  Si  Si8  1  0.43  0.4  0.48  1.0
  Cu  Cu9  1  0.43  0.77  0.94  1.0
  Cu  Cu10  1  0.62  0.71  0.94  1.0
  Cu  Cu11  1  0.81  0.49  0.83  1.0

Cu Cu Cu Cu Cu Cu Cu Cu Si Si Si Si
Cu Cu Cu Cu Cu Cu Cu Cu Si Si Si Si 0 1 o o + 0 10 o - o 1 8 o o o 1 9 o - o 2 5 o o o 2 10 o o o 3 6 o o o 3 8 o o + 4 5 + o o 4 10 + o o 5 10 o o o 6 7 o o o 6 8 o o + 7 8 o o + 8 9 o - o 8 9 + o o 8 11 o o o 9 11 - o o 9 11 o + o 9 10 o o o 10 11 - o o 10 11 o + o 
Cu2Si crystallizes in the triclinic P1 space group. There are eight inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a single-bond geometry to one Cu(2) and one Si(3) atom. The Cu(1)-Cu(2) bond length is 0.86 Å. The Cu(1)-Si(3) bond length is 2.49 Å. In the second Cu site, Cu(2) is bonded in a single-bond geometry to one Cu(1), one Si(1), and one Si(2) atom. The Cu(2)-Si(1) bond length is 2.47 Å. The Cu(2)-Si(2) bond length is 2.49 Å. In the third Cu site, Cu(3) is bonded in a distorted single-bond geometry to one Cu(4) and one Cu(6) atom. The Cu(3)-Cu(4) bond length is 1.32 Å. The Cu(3)-Cu(6) bond length is 0.81 Å. In the fourth Cu site, Cu(4) is bonded in a 2-coordinate geometry to one Cu(3) and one Cu(7) atom. The Cu(4)-Cu(7) bond length is 0.81 Å. In the fifth Cu site, Cu(5) is bonded in a distorted single-bond geometry to one Cu(6) and one Si(3) atom. The Cu(5)-Cu(6) bond length is 1.09 Å. The Cu(5)-Si(3) bond length is 2.29 Å. In the sixth Cu site, Cu(6) is bonded in a distorted bent 150 degrees geometry to one Cu(3) and one Cu(5) atom. In the seventh Cu site, Cu(7) is bonded in a bent 150 degrees geometry to one Cu(4) and one Cu(8) atom. The Cu(7)-Cu(8) bond length is 1.09 Å. In the eighth Cu site, Cu(8) is bonded in a distorted single-bond geometry to one Cu(7) and one Si(1) atom. The Cu(8)-Si(1) bond length is 2.29 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to one Cu(2), one Cu(8), one Si(4), and two equivalent Si(2) atoms. The Si(1)-Si(4) bond length is 2.33 Å. There is one shorter (2.62 Å) and one longer (2.73 Å) Si(1)-Si(2) bond length. In the second Si site, Si(2) is bonded in a 4-coordinate geometry to one Cu(2), one Si(3), and two equivalent Si(1) atoms. The Si(2)-Si(3) bond length is 2.33 Å. In the third Si site, Si(3) is bonded in a 5-coordinate geometry to one Cu(1), one Cu(5), one Si(2), and two equivalent Si(4) atoms. There is one shorter (2.62 Å) and one longer (2.73 Å) Si(3)-Si(4) bond length. In the fourth Si site, Si(4) is bonded in a 3-coordinate geometry to one Si(1) and two equivalent Si(3) atoms.