data_AlCrBr2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.16
_cell_length_b   5.16
_cell_length_c   5.16
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   AlCrBr2
_chemical_formula_sum   'Al1 Cr1 Br2'
_cell_volume   96.9
_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
  Al  Al0  1  0.0  0.0  0.0  1.0
  Cr  Cr3  1  0.82  0.82  0.82  1.0
  Br  Br1  1  0.65  0.65  0.65  1.0
  Br  Br2  1  0.47  0.47  0.47  1.0

data_AlCrBr2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.16
_cell_length_b   5.16
_cell_length_c   12.63
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   AlCrBr2
_chemical_formula_sum   'Al3 Cr3 Br6'
_cell_volume   290.71
_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
  Al  Al0  3  0.0  0.0  0.0  1.0
  Cr  Cr1  3  0.0  0.0  0.18  1.0
  Br  Br2  3  0.0  0.0  0.35  1.0
  Br  Br3  3  0.0  0.0  0.53  1.0

Al Cr Br Br
Al Cr Br Br 0 1 - - - 1 2 o o o 2 3 o o o 
CrAlBr2 crystallizes in the trigonal R3m space group. Cr(1) is bonded to one Al(1), one Br(1), and three equivalent Br(2) atoms to form distorted CrAlBr4 trigonal bipyramids that share corners with six equivalent Cr(1)AlBr4 trigonal bipyramids,  a cornercorner with one Br(2)Cr3Br trigonal pyramid, and corners with three equivalent Al(1)CrBr3 trigonal pyramids. The Cr(1)-Al(1) bond length is 2.24 Å. The Cr(1)-Br(1) bond length is 2.24 Å. All Cr(1)-Br(2) bond lengths are 2.99 Å. Al(1) is bonded to one Cr(1) and three equivalent Br(1) atoms to form AlCrBr3 trigonal pyramids that share corners with three equivalent Cr(1)AlBr4 trigonal bipyramids, corners with six equivalent Al(1)CrBr3 trigonal pyramids, and edges with three equivalent Br(2)Cr3Br trigonal pyramids. All Al(1)-Br(1) bond lengths are 2.99 Å. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded in a distorted single-bond geometry to one Cr(1), three equivalent Al(1), and one Br(2) atom. The Br(1)-Br(2) bond length is 2.24 Å. In the second Br site, Br(2) is bonded to three equivalent Cr(1) and one Br(1) atom to form BrCr3Br trigonal pyramids that share  a cornercorner with one Cr(1)AlBr4 trigonal bipyramid, corners with six equivalent Br(2)Cr3Br trigonal pyramids, and edges with three equivalent Al(1)CrBr3 trigonal pyramids.