data_Mg2BeBr
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.15
_cell_length_b   5.15
_cell_length_c   3.12
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2BeBr
_chemical_formula_sum   'Mg2 Be1 Br1'
_cell_volume   82.83
_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  Mg2  1  0.57  0.0  0.56  1.0
  Mg  Mg3  1  0.0  0.57  0.56  1.0
  Be  Be0  1  0.0  0.0  0.0  1.0
  Br  Br1  1  0.57  0.57  0.0  1.0

data_Mg2BeBr
_symmetry_space_group_name_H-M   Cm
_cell_length_a   7.28
_cell_length_b   7.28
_cell_length_c   3.12
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Mg2BeBr
_chemical_formula_sum   'Mg4 Be2 Br2'
_cell_volume   165.66
_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+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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  Mg0  4  0.29  0.29  0.56  1.0
  Be  Be1  2  0.0  0.0  0.0  1.0
  Br  Br2  2  0.07  0.5  0.0  1.0

Mg Mg Be Br
Mg Mg Be Br 0 2 o o + 0 2 + o o 0 2 + o + 0 3 o - o 0 3 o - + 0 3 o o + 0 1 + - o 0 0 o o + 1 3 - o o 1 3 - o + 1 3 o o + 1 2 o o + 1 2 o + o 1 2 o + + 1 1 o o + 2 3 - - o 2 2 o o + 3 3 o o + 
Mg2BeBr crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 5-coordinate geometry to two equivalent Be(1) and three equivalent Br(1) atoms. There is one shorter (2.58 Å) and one longer (2.81 Å) Mg(1)-Be(1) bond length. There are a spread of Mg(1)-Br(1) bond distances ranging from 2.58-3.26 Å. Be(1) is bonded in a 4-coordinate geometry to four equivalent Mg(1) atoms. Br(1) is bonded in a 6-coordinate geometry to six equivalent Mg(1) atoms.