data_MgCrB4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.03
_cell_length_b   4.03
_cell_length_c   4.03
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgCrB4
_chemical_formula_sum   'Mg1 Cr1 B4'
_cell_volume   46.17
_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  Mg5  1  0.0  0.0  0.0  1.0
  Cr  Cr4  1  0.27  0.27  0.27  1.0
  B  B0  1  0.11  0.58  0.58  1.0
  B  B1  1  0.58  0.58  0.11  1.0
  B  B2  1  0.58  0.11  0.58  1.0
  B  B3  1  0.11  0.11  0.11  1.0

data_MgCrB4
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.03
_cell_length_b   4.03
_cell_length_c   9.86
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   MgCrB4
_chemical_formula_sum   'Mg3 Cr3 B12'
_cell_volume   138.52
_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  0.73  1.0
  B  B2  9  0.18  0.82  0.24  1.0
  B  B3  3  0.0  0.0  0.89  1.0

Mg Cr B B B B
Mg Cr B B B B 0 5 o o o 0 2 o o - 0 2 o - o 0 3 o - o 0 3 - o o 0 4 o o - 0 4 - o o 1 5 o o o 1 2 o o o 1 4 o o o 1 3 o o o 2 5 o o + 2 5 o + o 2 4 - + o 2 4 o o o 2 3 - o + 2 3 o o o 3 4 o o o 3 4 o + - 3 5 o + o 3 5 + o o 4 5 o o + 4 5 + o o 
MgCrB4 is Copper structured and crystallizes in the trigonal R3m space group. The structure is zero-dimensional and consists of three MgCrB4 clusters. Mg(1) is bonded in a single-bond geometry to one B(2) atom. The Mg(1)-B(2) bond length is 1.10 Å. Cr(1) is bonded in a 4-coordinate geometry to one B(2) and three equivalent B(1) atoms. The Cr(1)-B(2) bond length is 1.57 Å. All Cr(1)-B(1) bond lengths are 1.88 Å. There are two inequivalent B sites. In the first B site, B(2) is bonded in a distorted single-bond geometry to one Mg(1) and one Cr(1) atom. In the second B site, B(1) is bonded in a distorted single-bond geometry to one Cr(1) atom.