data_MgCrBr2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.05
_cell_length_b   5.05
_cell_length_c   5.05
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgCrBr2
_chemical_formula_sum   'Mg1 Cr1 Br2'
_cell_volume   91.29
_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
  Mg  Mg3  1  0.0  0.0  0.0  1.0
  Cr  Cr2  1  0.57  0.57  0.57  1.0
  Br  Br0  1  0.36  0.36  0.36  1.0
  Br  Br1  1  0.79  0.79  0.79  1.0

data_MgCrBr2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.05
_cell_length_b   5.05
_cell_length_c   12.38
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   MgCrBr2
_chemical_formula_sum   'Mg3 Cr3 Br6'
_cell_volume   273.88
_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
  Mg  Mg0  3  0.0  0.0  0.0  1.0
  Cr  Cr1  3  0.0  0.0  0.43  1.0
  Br  Br2  3  0.0  0.0  0.21  1.0
  Br  Br3  3  0.0  0.0  0.64  1.0

Mg Cr Br Br
MgCrBr2 is Heusler structured and crystallizes in the trigonal R3m space group. Mg(1) is bonded in a 4-coordinate geometry to one Br(2) and three equivalent Br(1) atoms. The Mg(1)-Br(2) bond length is 2.64 Å. All Mg(1)-Br(1) bond lengths are 2.94 Å. Cr(1) is bonded in a distorted linear geometry to one Br(1) and one Br(2) atom. The Cr(1)-Br(1) bond length is 2.64 Å. The Cr(1)-Br(2) bond length is 2.64 Å. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded to three equivalent Mg(1) and one Cr(1) atom to form distorted corner-sharing BrMg3Cr trigonal pyramids. In the second Br site, Br(2) is bonded in a distorted linear geometry to one Mg(1) and one Cr(1) atom.