data_BaAl2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.91
_cell_length_b   3.91
_cell_length_c   6.87
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   BaAl2Se
_chemical_formula_sum   'Ba1 Al2 Se1'
_cell_volume   105.17
_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
  Ba  Ba2  1  0.96  0.96  0.49  1.0
  Al  Al0  1  0.96  0.96  0.22  1.0
  Al  Al1  1  0.0  0.0  0.13  1.0
  Se  Se3  1  0.0  0.0  0.46  1.0

data_BaAl2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.53
_cell_length_b   5.53
_cell_length_c   6.87
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   BaAl2Se
_chemical_formula_sum   'Ba2 Al4 Se2'
_cell_volume   210.34
_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
  Ba  Ba0  2  0.46  0.5  0.49  1.0
  Al  Al1  2  0.0  0.0  0.13  1.0
  Al  Al2  2  0.46  0.5  0.22  1.0
  Se  Se3  2  0.0  0.0  0.46  1.0

Ba Al Al Se
BaAl2Se crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two BaAl2Se clusters. Ba(1) is bonded in a single-bond geometry to one Se(1) atom. The Ba(1)-Se(1) bond length is 0.35 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a bent 150 degrees geometry to one Al(2) and one Se(1) atom. The Al(1)-Al(2) bond length is 0.68 Å. The Al(1)-Se(1) bond length is 1.62 Å. In the second Al site, Al(2) is bonded in a single-bond geometry to one Al(1) atom. Se(1) is bonded in a distorted single-bond geometry to one Ba(1) and one Al(1) atom.