data_MnBe2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.79
_cell_length_b   3.79
_cell_length_c   3.31
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MnBe2Se
_chemical_formula_sum   'Mn1 Be2 Se1'
_cell_volume   47.45
_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
  Mn  Mn2  1  0.0  0.0  0.0  1.0
  Be  Be0  1  0.89  0.0  0.65  1.0
  Be  Be1  1  0.0  0.89  0.65  1.0
  Se  Se3  1  0.89  0.89  0.0  1.0

data_MnBe2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.36
_cell_length_b   5.36
_cell_length_c   3.31
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   MnBe2Se
_chemical_formula_sum   'Mn2 Be4 Se2'
_cell_volume   94.9
_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
  Mn  Mn0  2  0.0  0.0  0.0  1.0
  Be  Be1  4  0.45  0.45  0.65  1.0
  Se  Se2  2  0.39  0.5  0.0  1.0

Mn Be Be Se
Mn Be Be Se 0 3 - - o 1 2 + - o 
Be2MnSe is alpha Po structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two Be2MnSe clusters. Be(1) is bonded in a 2-coordinate geometry to one Be(1) and one Se(1) atom. The Be(1)-Be(1) bond length is 0.57 Å. The Be(1)-Se(1) bond length is 1.21 Å. Mn(1) is bonded in a single-bond geometry to one Se(1) atom. The Mn(1)-Se(1) bond length is 0.57 Å. Se(1) is bonded in a single-bond geometry to two equivalent Be(1) and one Mn(1) atom.