data_AlSi2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.61
_cell_length_b   4.61
_cell_length_c   4.61
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   AlSi2Se
_chemical_formula_sum   'Al1 Si2 Se1'
_cell_volume   69.48
_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
  Al  Al0  1  0.0  0.0  0.0  1.0
  Si  Si2  1  0.63  0.63  0.63  1.0
  Si  Si3  1  0.89  0.89  0.89  1.0
  Se  Se1  1  0.26  0.26  0.26  1.0

data_AlSi2Se
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.61
_cell_length_b   4.61
_cell_length_c   11.3
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   AlSi2Se
_chemical_formula_sum   'Al3 Si6 Se3'
_cell_volume   208.45
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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
  Al  Al0  3  0.0  0.0  0.0  1.0
  Si  Si1  3  0.0  0.0  0.11  1.0
  Si  Si2  3  0.0  0.0  0.37  1.0
  Se  Se3  3  0.0  0.0  0.74  1.0

Al Si Si Se
Al Si Si Se 0 2 - - - 0 1 o - - 0 1 - o - 0 1 - - o 0 3 o o o 0 3 o o - 0 3 o - o 0 3 - o o 1 3 o o + 1 3 o + o 1 3 + o o 1 2 - o o 1 2 o - o 1 2 o o - 1 2 o o o 2 3 + + o 2 3 + o + 2 3 o + + 
AlSi2Se crystallizes in the trigonal R3m space group. Al(1) is bonded in a single-bond geometry to one Si(2), three equivalent Si(1), and four equivalent Se(1) atoms. The Al(1)-Si(2) bond length is 1.19 Å. All Al(1)-Si(1) bond lengths are 2.69 Å. There are three shorter (2.78 Å) and one longer (2.97 Å) Al(1)-Se(1) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a distorted hexagonal planar geometry to three equivalent Al(1) and three equivalent Se(1) atoms. All Si(1)-Se(1) bond lengths are 2.69 Å. In the second Si site, Si(2) is bonded in a single-bond geometry to one Al(1) and three equivalent Se(1) atoms. All Si(2)-Se(1) bond lengths are 2.69 Å. Se(1) is bonded in a 10-coordinate geometry to four equivalent Al(1), three equivalent Si(1), and three equivalent Si(2) atoms.