data_Si3Sb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.22
_cell_length_b   3.22
_cell_length_c   7.01
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si3Sb
_chemical_formula_sum   'Si3 Sb1'
_cell_volume   72.88
_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
  Si  Si1  1  0.61  0.61  0.29  1.0
  Si  Si2  1  0.0  0.0  0.0  1.0
  Si  Si3  1  0.61  0.61  0.72  1.0
  Sb  Sb0  1  0.0  0.0  0.5  1.0

data_Si3Sb
_symmetry_space_group_name_H-M   Amm2
_cell_length_a   7.01
_cell_length_b   4.56
_cell_length_c   4.56
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   38
_chemical_formula_structural   Si3Sb
_chemical_formula_sum   'Si6 Sb2'
_cell_volume   145.76
_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, y, z'
  4  'x, -y, z'
  5  'x, y+1/2, z+1/2'
  6  '-x, -y+1/2, z+1/2'
  7  '-x, y+1/2, z+1/2'
  8  'x, -y+1/2, z+1/2'
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
  Si  Si0  4  0.28  0.0  0.61  1.0
  Si  Si1  2  0.0  0.0  0.0  1.0
  Sb  Sb2  2  0.5  0.0  0.0  1.0

Si Si Si Sb
Si Si Si Sb 0 3 o o o 0 3 o + o 0 3 + o o 0 3 + + o 0 1 o + o 0 1 + o o 0 1 + + o 0 1 o o o 0 0 + o o 0 0 o + o 0 2 o o o 1 2 - - - 1 2 - o - 1 2 o - - 1 2 o o - 1 1 + o o 1 1 o + o 1 3 o o - 2 3 o o o 2 3 o + o 2 3 + o o 2 3 + + o 2 2 + o o 2 2 o + o 
Si3Sb crystallizes in the monoclinic Cm space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 1-coordinate geometry to one Si(2) and three equivalent Sb(1) atoms. The Si(1)-Si(2) bond length is 2.67 Å. There is one shorter (2.33 Å) and two longer (2.79 Å) Si(1)-Sb(1) bond lengths. In the second Si site, Si(2) is bonded in an L-shaped geometry to one Si(1) and one Si(3) atom. The Si(2)-Si(3) bond length is 2.63 Å. In the third Si site, Si(3) is bonded in a 1-coordinate geometry to one Si(2) and three equivalent Sb(1) atoms. There is one shorter (2.33 Å) and two longer (2.79 Å) Si(3)-Sb(1) bond lengths. Sb(1) is bonded in a 6-coordinate geometry to three equivalent Si(1) and three equivalent Si(3) atoms.