data_SiBiBr2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.21
_cell_length_b   5.21
_cell_length_c   5.21
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   SiBiBr2
_chemical_formula_sum   'Si1 Bi1 Br2'
_cell_volume   99.97
_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  Si3  1  0.0  0.0  0.0  1.0
  Bi  Bi0  1  0.84  0.84  0.84  1.0
  Br  Br1  1  0.53  0.53  0.53  1.0
  Br  Br2  1  0.68  0.68  0.68  1.0

data_SiBiBr2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.21
_cell_length_b   5.21
_cell_length_c   12.76
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   SiBiBr2
_chemical_formula_sum   'Si3 Bi3 Br6'
_cell_volume   299.92
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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  3  0.0  0.0  0.0  1.0
  Bi  Bi1  3  0.0  0.0  0.16  1.0
  Br  Br2  3  0.0  0.0  0.32  1.0
  Br  Br3  3  0.0  0.0  0.47  1.0

Si Bi Br Br
Si Bi Br Br 0 1 - - - 1 3 o o o 2 3 o o o 
SiBiBr2 crystallizes in the trigonal R3m space group. Si(1) is bonded to one Bi(1) and three equivalent Br(2) atoms to form distorted SiBiBr3 trigonal pyramids that share corners with three equivalent Bi(1)SiBr4 trigonal bipyramids, corners with six equivalent Si(1)BiBr3 trigonal pyramids, and edges with three equivalent Br(1)Bi3Br trigonal pyramids. The Si(1)-Bi(1) bond length is 2.02 Å. All Si(1)-Br(2) bond lengths are 3.02 Å. Bi(1) is bonded to one Si(1), one Br(2), and three equivalent Br(1) atoms to form distorted BiSiBr4 trigonal bipyramids that share corners with six equivalent Bi(1)SiBr4 trigonal bipyramids,  a cornercorner with one Br(1)Bi3Br trigonal pyramid, and corners with three equivalent Si(1)BiBr3 trigonal pyramids. The Bi(1)-Br(2) bond length is 2.02 Å. All Bi(1)-Br(1) bond lengths are 3.02 Å. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded to three equivalent Bi(1) and one Br(2) atom to form BrBi3Br trigonal pyramids that share  a cornercorner with one Bi(1)SiBr4 trigonal bipyramid, corners with six equivalent Br(1)Bi3Br trigonal pyramids, and edges with three equivalent Si(1)BiBr3 trigonal pyramids. The Br(1)-Br(2) bond length is 2.02 Å. In the second Br site, Br(2) is bonded in a distorted single-bond geometry to three equivalent Si(1), one Bi(1), and one Br(1) atom.