data_CaAlSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.28
_cell_length_b   7.28
_cell_length_c   7.28
_cell_angle_alpha   31.52
_cell_angle_beta   31.52
_cell_angle_gamma   31.52
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaAlSe2
_chemical_formula_sum   'Ca1 Al1 Se2'
_cell_volume   93.75
_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
  Ca  Ca1  1  0.0  0.0  0.37  1.0
  Al  Al0  1  0.0  0.0  0.0  1.0
  Se  Se2  1  0.0  0.0  0.35  1.0
  Se  Se3  1  0.0  0.0  0.4  1.0

data_CaAlSe2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.85
_cell_length_b   3.96
_cell_length_c   7.28
_cell_angle_alpha   90.0
_cell_angle_beta   108.28
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   CaAlSe2
_chemical_formula_sum   'Ca2 Al2 Se4'
_cell_volume   187.5
_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
  Ca  Ca0  2  0.0  0.0  0.63  1.0
  Al  Al1  2  0.0  0.0  0.0  1.0
  Se  Se2  2  0.0  0.0  0.6  1.0
  Se  Se3  2  0.0  0.0  0.65  1.0

Ca Al Se Se
CaAlSe2 is Cyanogen Chloride-like structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two CaAlSe2 clusters. Ca(1) is bonded in a linear geometry to one Se(1) and one Se(2) atom. The Ca(1)-Se(1) bond length is 0.18 Å. The Ca(1)-Se(2) bond length is 0.18 Å. Al(1) is bonded in a single-bond geometry to one Se(1) atom. The Al(1)-Se(1) bond length is 2.53 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a single-bond geometry to one Ca(1) and one Al(1) atom. In the second Se site, Se(2) is bonded in a single-bond geometry to one Ca(1) atom.