data_AlSiSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.51
_cell_length_b   4.51
_cell_length_c   4.51
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   AlSiSe
_chemical_formula_sum   'Al1 Si1 Se1'
_cell_volume   64.86
_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  0.19  0.19  0.19  1.0
  Se  Se1  1  0.59  0.59  0.59  1.0

data_AlSiSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.51
_cell_length_b   4.51
_cell_length_c   11.05
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   AlSiSe
_chemical_formula_sum   'Al3 Si3 Se3'
_cell_volume   194.57
_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  0.81  1.0
  Se  Se2  3  0.0  0.0  0.41  1.0

Al Si Se
AlSiSe crystallizes in the trigonal R3m space group. Al(1) is bonded to one Si(1) and three equivalent Se(1) atoms to form AlSiSe3 tetrahedra that share corners with three equivalent Si(1)AlSe3 tetrahedra, corners with six equivalent Al(1)SiSe3 tetrahedra, and edges with three equivalent Si(1)AlSe3 tetrahedra. The Al(1)-Si(1) bond length is 2.09 Å. All Al(1)-Se(1) bond lengths are 2.72 Å. Si(1) is bonded to one Al(1) and three equivalent Se(1) atoms to form distorted SiAlSe3 tetrahedra that share corners with three equivalent Al(1)SiSe3 tetrahedra, corners with six equivalent Si(1)AlSe3 tetrahedra, and edges with three equivalent Al(1)SiSe3 tetrahedra. All Si(1)-Se(1) bond lengths are 2.72 Å. Se(1) is bonded in a distorted hexagonal planar geometry to three equivalent Al(1) and three equivalent Si(1) atoms.