data_Be2CuSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.48
_cell_length_b   2.48
_cell_length_c   7.05
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Be2CuSi
_chemical_formula_sum   'Be2 Cu1 Si1'
_cell_volume   43.32
_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
  Be  Be0  1  0.24  0.24  0.9  1.0
  Be  Be1  1  0.24  0.24  0.15  1.0
  Cu  Cu2  1  0.0  0.0  0.53  1.0
  Si  Si3  1  0.0  0.0  0.0  1.0

data_Be2CuSi
_symmetry_space_group_name_H-M   Cm
_cell_length_a   3.51
_cell_length_b   3.51
_cell_length_c   7.05
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Be2CuSi
_chemical_formula_sum   'Be4 Cu2 Si2'
_cell_volume   86.63
_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
  Be  Be0  2  0.24  0.0  0.15  1.0
  Be  Be1  2  0.24  0.0  0.9  1.0
  Si  Si2  2  0.0  0.0  0.0  1.0
  Cu  Cu3  2  0.0  0.0  0.53  1.0

Be Be Cu Si
Be Be Cu Si 0 3 o o + 0 2 o o o 1 3 o o o 1 2 o o o 2 2 + o o 2 2 o + o 
Be2CuSi crystallizes in the monoclinic Cm space group. There are two inequivalent Be sites. In the first Be site, Be(1) is bonded in a single-bond geometry to one Cu(1) and one Si(1) atom. The Be(1)-Cu(1) bond length is 2.77 Å. The Be(1)-Si(1) bond length is 1.10 Å. In the second Be site, Be(2) is bonded in a single-bond geometry to one Cu(1) and one Si(1) atom. The Be(2)-Cu(1) bond length is 2.77 Å. The Be(2)-Si(1) bond length is 1.35 Å. Cu(1) is bonded to one Be(1), one Be(2), and four equivalent Cu(1) atoms to form a mixture of edge and corner-sharing CuBe2Cu4 octahedra. The corner-sharing octahedra are not tilted. All Cu(1)-Cu(1) bond lengths are 2.48 Å. Si(1) is bonded in a distorted L-shaped geometry to one Be(1) and one Be(2) atom.