data_Ta2AsSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.56
_cell_length_b   4.56
_cell_length_c   4.56
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ta2AsSe
_chemical_formula_sum   'Ta2 As1 Se1'
_cell_volume   67.0
_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
  Ta  Ta2  1  0.84  0.84  0.84  1.0
  Ta  Ta3  1  0.61  0.61  0.61  1.0
  As  As0  1  0.0  0.0  0.0  1.0
  Se  Se1  1  0.22  0.22  0.22  1.0

data_Ta2AsSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.56
_cell_length_b   4.56
_cell_length_c   11.17
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Ta2AsSe
_chemical_formula_sum   'Ta6 As3 Se3'
_cell_volume   201.01
_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
  Ta  Ta0  3  0.0  0.0  0.16  1.0
  Ta  Ta1  3  0.0  0.0  0.39  1.0
  As  As2  3  0.0  0.0  0.0  1.0
  Se  Se3  3  0.0  0.0  0.78  1.0

Ta Ta As Se
Ta Ta As Se 0 2 + + + 0 1 o + o 0 1 + o o 0 1 o o + 0 1 o o o 0 3 + + o 0 3 + o + 0 3 o + + 1 3 o o + 1 3 o + o 1 3 + o o 1 2 o + + 1 2 + o + 1 2 + + o 2 3 o o o 2 3 o o - 2 3 - o o 2 3 o - o 
Ta2AsSe crystallizes in the trigonal R3m space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a distorted single-bond geometry to one Ta(2), one As(1), and three equivalent Se(1) atoms. The Ta(1)-Ta(2) bond length is 2.50 Å. The Ta(1)-As(1) bond length is 1.84 Å. All Ta(1)-Se(1) bond lengths are 2.70 Å. In the second Ta site, Ta(2) is bonded in a 7-coordinate geometry to one Ta(1), three equivalent As(1), and three equivalent Se(1) atoms. All Ta(2)-As(1) bond lengths are 2.70 Å. All Ta(2)-Se(1) bond lengths are 2.70 Å. As(1) is bonded in a distorted single-bond geometry to one Ta(1), three equivalent Ta(2), and four equivalent Se(1) atoms. There is one shorter (2.50 Å) and three longer (2.90 Å) As(1)-Se(1) bond lengths. Se(1) is bonded in a 10-coordinate geometry to three equivalent Ta(1), three equivalent Ta(2), and four equivalent As(1) atoms.