data_BaTiSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.23
_cell_length_b   5.23
_cell_length_c   5.23
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   BaTiSe2
_chemical_formula_sum   'Ba1 Ti1 Se2'
_cell_volume   100.99
_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  Ba0  1  0.54  0.54  0.54  1.0
  Ti  Ti3  1  0.0  0.0  0.0  1.0
  Se  Se1  1  0.85  0.85  0.85  1.0
  Se  Se2  1  0.7  0.7  0.7  1.0

data_BaTiSe2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.23
_cell_length_b   5.23
_cell_length_c   12.8
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   BaTiSe2
_chemical_formula_sum   'Ba3 Ti3 Se6'
_cell_volume   302.96
_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
  Ba  Ba0  3  0.0  0.0  0.46  1.0
  Ti  Ti1  3  0.0  0.0  0.0  1.0
  Se  Se2  3  0.0  0.0  0.15  1.0
  Se  Se3  3  0.0  0.0  0.3  1.0

Ba Ti Se Se
BaTiSe2 crystallizes in the trigonal R3m space group. Ba(1) is bonded in a distorted single-bond geometry to one Se(2) and three equivalent Se(1) atoms. The Ba(1)-Se(2) bond length is 1.95 Å. All Ba(1)-Se(1) bond lengths are 3.04 Å. Ti(1) is bonded in a distorted single-bond geometry to one Se(1) atom. The Ti(1)-Se(1) bond length is 1.95 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Ba(1), one Ti(1), and one Se(2) atom to form distorted corner-sharing SeBa3TiSe trigonal bipyramids. The Se(1)-Se(2) bond length is 1.95 Å. In the second Se site, Se(2) is bonded in a distorted single-bond geometry to one Ba(1) and one Se(1) atom.