data_SrTaAlTl
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.18
_cell_length_b   5.18
_cell_length_c   5.18
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   SrTaAlTl
_chemical_formula_sum   'Sr1 Ta1 Al1 Tl1'
_cell_volume   98.56
_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
  Sr  Sr1  1  0.67  0.67  0.67  1.0
  Ta  Ta2  1  0.83  0.83  0.83  1.0
  Al  Al0  1  0.0  0.0  0.0  1.0
  Tl  Tl3  1  0.5  0.5  0.5  1.0

data_SrTaAlTl
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.18
_cell_length_b   5.18
_cell_length_c   12.7
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   SrTaAlTl
_chemical_formula_sum   'Sr3 Ta3 Al3 Tl3'
_cell_volume   295.68
_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
  Sr  Sr0  3  0.0  0.0  0.33  1.0
  Ta  Ta1  3  0.0  0.0  0.17  1.0
  Al  Al2  3  0.0  0.0  0.0  1.0
  Tl  Tl3  3  0.0  0.0  0.5  1.0

Sr Ta Al Tl
Sr Ta Al Tl 0 3 o o o 0 1 o o o 1 2 + + + 
SrTaTlAl crystallizes in the trigonal R3m space group. Sr(1) is bonded to one Ta(1), one Tl(1), and three equivalent Al(1) atoms to form distorted SrTaAl3Tl trigonal bipyramids that share corners with six equivalent Sr(1)TaAl3Tl trigonal bipyramids and  a cornercorner with one Al(1)Sr3Ta trigonal pyramid. The Sr(1)-Ta(1) bond length is 2.12 Å. The Sr(1)-Tl(1) bond length is 2.12 Å. All Sr(1)-Al(1) bond lengths are 2.99 Å. Ta(1) is bonded in a 5-coordinate geometry to one Sr(1), three equivalent Tl(1), and one Al(1) atom. All Ta(1)-Tl(1) bond lengths are 2.99 Å. The Ta(1)-Al(1) bond length is 2.12 Å. Tl(1) is bonded in a distorted single-bond geometry to one Sr(1) and three equivalent Ta(1) atoms. Al(1) is bonded to three equivalent Sr(1) and one Ta(1) atom to form AlSr3Ta trigonal pyramids that share  a cornercorner with one Sr(1)TaAl3Tl trigonal bipyramid and corners with six equivalent Al(1)Sr3Ta trigonal pyramids.