data_MgBe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.12
_cell_length_b   5.12
_cell_length_c   5.12
_cell_angle_alpha   148.44
_cell_angle_beta   148.44
_cell_angle_gamma   45.23
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgBe2
_chemical_formula_sum   'Mg1 Be2'
_cell_volume   36.71
_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  0.0  0.0  0.0  1.0
  Be  Be0  1  0.0  0.0  0.61  1.0
  Be  Be1  1  0.0  0.0  0.85  1.0

data_MgBe2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   3.94
_cell_length_b   3.94
_cell_length_c   5.12
_cell_angle_alpha   90.0
_cell_angle_beta   112.61
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   MgBe2
_chemical_formula_sum   'Mg2 Be4'
_cell_volume   73.41
_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  2  0.0  0.0  0.0  1.0
  Be  Be1  2  0.11  0.5  0.61  1.0
  Be  Be2  2  0.35  0.5  0.85  1.0

Mg Be Be
Mg Be Be 0 2 o o - 1 2 o o o 
MgBe2 crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two MgBe2 clusters. Mg(1) is bonded in a single-bond geometry to one Be(2) atom. The Mg(1)-Be(2) bond length is 0.78 Å. There are two inequivalent Be sites. In the first Be site, Be(1) is bonded in a single-bond geometry to one Be(2) atom. The Be(1)-Be(2) bond length is 1.21 Å. In the second Be site, Be(2) is bonded in a distorted single-bond geometry to one Mg(1) and one Be(1) atom.