data_FeSnSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.62
_cell_length_b   4.62
_cell_length_c   4.62
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   FeSnSe
_chemical_formula_sum   'Fe1 Sn1 Se1'
_cell_volume   69.72
_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
  Fe  Fe0  1  0.0  0.0  0.0  1.0
  Sn  Sn2  1  0.27  0.27  0.27  1.0
  Se  Se1  1  0.63  0.63  0.63  1.0

data_FeSnSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.62
_cell_length_b   4.62
_cell_length_c   11.32
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   FeSnSe
_chemical_formula_sum   'Fe3 Sn3 Se3'
_cell_volume   209.17
_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
  Fe  Fe0  3  0.0  0.0  0.0  1.0
  Sn  Sn1  3  0.0  0.0  0.73  1.0
  Se  Se2  3  0.0  0.0  0.37  1.0

Fe Sn Se
FeSnSe crystallizes in the trigonal R3m space group. Fe(1) is bonded to four equivalent Sn(1) and three equivalent Se(1) atoms to form distorted FeSn4Se3 hexagonal pyramids that share corners with three equivalent Sn(1)Fe4Se3 hexagonal pyramids, corners with six equivalent Fe(1)Sn4Se3 hexagonal pyramids, edges with three equivalent Sn(1)Fe4Se3 hexagonal pyramids, and edges with six equivalent Fe(1)Sn4Se3 hexagonal pyramids. There are three shorter (2.77 Å) and one longer (3.02 Å) Fe(1)-Sn(1) bond length. All Fe(1)-Se(1) bond lengths are 2.69 Å. Sn(1) is bonded to four equivalent Fe(1) and three equivalent Se(1) atoms to form distorted SnFe4Se3 hexagonal pyramids that share corners with three equivalent Fe(1)Sn4Se3 hexagonal pyramids, corners with six equivalent Sn(1)Fe4Se3 hexagonal pyramids, edges with three equivalent Fe(1)Sn4Se3 hexagonal pyramids, and edges with six equivalent Sn(1)Fe4Se3 hexagonal pyramids. All Sn(1)-Se(1) bond lengths are 2.69 Å. Se(1) is bonded in a hexagonal planar geometry to three equivalent Fe(1) and three equivalent Sn(1) atoms.