data_BeTlSn2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.19
_cell_length_b   5.19
_cell_length_c   5.19
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   BeTlSn2
_chemical_formula_sum   'Be1 Tl1 Sn2'
_cell_volume   98.77
_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
  Be  Be0  1  0.0  0.0  0.0  1.0
  Tl  Tl3  1  0.5  0.5  0.5  1.0
  Sn  Sn1  1  0.67  0.67  0.67  1.0
  Sn  Sn2  1  0.83  0.83  0.83  1.0

data_BeTlSn2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.19
_cell_length_b   5.19
_cell_length_c   12.71
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   BeTlSn2
_chemical_formula_sum   'Be3 Tl3 Sn6'
_cell_volume   296.32
_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
  Be  Be0  3  0.0  0.0  0.0  1.0
  Tl  Tl1  3  0.0  0.0  0.5  1.0
  Sn  Sn2  3  0.0  0.0  0.17  1.0
  Sn  Sn3  3  0.0  0.0  0.33  1.0

Be Tl Sn Sn
BeTlSn2 crystallizes in the trigonal R3m space group. Be(1) is bonded in a distorted single-bond geometry to one Sn(2) and three equivalent Sn(1) atoms. The Be(1)-Sn(2) bond length is 2.10 Å. All Be(1)-Sn(1) bond lengths are 3.00 Å. Tl(1) is bonded to one Sn(1) and three equivalent Sn(2) atoms to form distorted TlSn4 trigonal pyramids that share  a cornercorner with one Sn(2)BeTl3Sn trigonal bipyramid, corners with three equivalent Sn(1)Be3TlSn trigonal bipyramids, and corners with six equivalent Tl(1)Sn4 trigonal pyramids. The Tl(1)-Sn(1) bond length is 2.10 Å. All Tl(1)-Sn(2) bond lengths are 3.00 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to three equivalent Be(1), one Tl(1), and one Sn(2) atom to form distorted SnBe3TlSn trigonal bipyramids that share corners with six equivalent Sn(1)Be3TlSn trigonal bipyramids, corners with three equivalent Tl(1)Sn4 trigonal pyramids, and edges with three equivalent Sn(2)BeTl3Sn trigonal bipyramids. The Sn(1)-Sn(2) bond length is 2.10 Å. In the second Sn site, Sn(2) is bonded to one Be(1), three equivalent Tl(1), and one Sn(1) atom to form distorted SnBeTl3Sn trigonal bipyramids that share corners with six equivalent Sn(2)BeTl3Sn trigonal bipyramids,  a cornercorner with one Tl(1)Sn4 trigonal pyramid, and edges with three equivalent Sn(1)Be3TlSn trigonal bipyramids.