The material described by Sm2Se3 crystallizes in the tetragonal I-42d space group. There are three inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to two equivalent Se(2), three equivalent Se(1), and three equivalent Se(3) atoms. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to two equivalent Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. In the third Sm site, Sm(3) is bonded to two equivalent Se(1), two equivalent Se(3), and four equivalent Se(2) atoms to form distorted edge-sharing SmSe8 hexagonal bipyramids. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Sm(3), two equivalent Sm(2), and three equivalent Sm(1) atoms to form distorted SeSm6 octahedra that share corners with three equivalent Se(1)Sm6 octahedra, corners with seven equivalent Se(3)Sm5 square pyramids, corners with five equivalent Se(2)Sm5 trigonal bipyramids, edges with two equivalent Se(1)Sm6 octahedra,  an edgeedge with one Se(3)Sm5 square pyramid, edges with three equivalent Se(2)Sm5 trigonal bipyramids, faces with two equivalent Se(1)Sm6 octahedra, faces with two equivalent Se(3)Sm5 square pyramids, and  a faceface with one Se(2)Sm5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 18-49°. In the second Se site, Se(2) is bonded to one Sm(2), two equivalent Sm(1), and two equivalent Sm(3) atoms to form distorted SeSm5 trigonal bipyramids that share corners with five equivalent Se(1)Sm6 octahedra, corners with four equivalent Se(3)Sm5 square pyramids, corners with four equivalent Se(2)Sm5 trigonal bipyramids, edges with three equivalent Se(1)Sm6 octahedra, edges with four equivalent Se(3)Sm5 square pyramids,  an edgeedge with one Se(2)Sm5 trigonal bipyramid,  a faceface with one Se(1)Sm6 octahedra, and  a faceface with one Se(2)Sm5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 23-50°. In the third Se site, Se(3) is bonded to one Sm(2), one Sm(3), and three equivalent Sm(1) atoms to form distorted SeSm5 square pyramids that share corners with seven equivalent Se(1)Sm6 octahedra, corners with five equivalent Se(3)Sm5 square pyramids, corners with four equivalent Se(2)Sm5 trigonal bipyramids,  an edgeedge with one Se(1)Sm6 octahedra, edges with four equivalent Se(2)Sm5 trigonal bipyramids, faces with two equivalent Se(1)Sm6 octahedra, and  a faceface with one Se(3)Sm5 square pyramid. The corner-sharing octahedral tilt angles range from 14-54°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sm2Se3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.647
_cell_length_b   14.647
_cell_length_c   14.647
_cell_angle_alpha   144.888
_cell_angle_beta   144.888
_cell_angle_gamma   50.501
_symmetry_Int_Tables_number   1
_cell_volume   1034.299
_cell_formula_units_Z   8
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
  Sm  Sm0  1  0.846  0.952  0.376  1.0
  Sm  Sm1  1  0.575  0.470  0.624  1.0
  Sm  Sm2  1  0.166  0.166  1.000  1.0
  Sm  Sm3  1  0.875  0.506  0.131  1.0
  Sm  Sm4  1  0.175  0.298  0.395  1.0
  Sm  Sm5  1  0.584  0.084  0.500  1.0
  Sm  Sm6  1  0.904  0.780  0.605  1.0
  Sm  Sm7  1  0.375  0.744  0.869  1.0
  Sm  Sm8  1  0.220  0.825  0.123  1.0
  Sm  Sm9  1  0.916  0.416  0.500  1.0
  Sm  Sm10  1  0.494  0.625  0.369  1.0
  Sm  Sm11  1  0.256  0.125  0.631  1.0
  Sm  Sm12  1  0.702  0.096  0.876  1.0
  Sm  Sm13  1  0.834  0.834  0.000  1.0
  Sm  Sm14  1  0.530  0.154  0.106  1.0
  Sm  Sm15  1  0.048  0.425  0.894  1.0
  Se  Se16  1  0.506  0.115  0.254  1.0
  Se  Se17  1  0.074  0.827  0.611  1.0
  Se  Se18  1  0.862  0.252  0.746  1.0
  Se  Se19  1  0.888  0.135  0.891  1.0
  Se  Se20  1  0.244  0.998  0.109  1.0
  Se  Se21  1  0.676  0.787  0.253  1.0
  Se  Se22  1  0.216  0.463  0.389  1.0
  Se  Se23  1  0.842  0.438  0.246  1.0
  Se  Se24  1  0.534  0.423  0.747  1.0
  Se  Se25  1  0.404  0.158  0.596  1.0
  Se  Se26  1  0.192  0.596  0.754  1.0
  Se  Se27  1  0.213  0.466  0.889  1.0
  Se  Se28  1  0.577  0.324  0.111  1.0
  Se  Se29  1  0.002  0.112  0.246  1.0
  Se  Se30  1  0.562  0.808  0.404  1.0
  Se  Se31  1  0.173  0.784  0.246  1.0
  Se  Se32  1  0.865  0.756  0.754  1.0
  Se  Se33  1  0.748  0.494  0.609  1.0
  Se  Se34  1  0.537  0.926  0.754  1.0
  Se  Se35  1  0.558  0.812  0.904  1.0
  Se  Se36  1  0.908  0.654  0.096  1.0
  Se  Se37  1  0.346  0.442  0.254  1.0
  Se  Se38  1  0.885  0.138  0.391  1.0
  Se  Se39  1  0.188  0.092  0.746  1.0
[/CIF]
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The material described by Sm2Se3 crystallizes in the tetragonal I-42d space group. There are three inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to two equivalent Se(2), three equivalent Se(1), and three equivalent Se(3) atoms. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to two equivalent Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. In the third Sm site, Sm(3) is bonded to two equivalent Se(1), two equivalent Se(3), and four equivalent Se(2) atoms to form distorted edge-sharing SmSe8 hexagonal bipyramids. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Sm(3), two equivalent Sm(2), and three equivalent Sm(1) atoms to form distorted SeSm6 octahedra that share corners with three equivalent Se(1)Sm6 octahedra, corners with seven equivalent Se(3)Sm5 square pyramids, corners with five equivalent Se(2)Sm5 trigonal bipyramids, edges with two equivalent Se(1)Sm6 octahedra,  an edgeedge with one Se(3)Sm5 square pyramid, edges with three equivalent Se(2)Sm5 trigonal bipyramids, faces with two equivalent Se(1)Sm6 octahedra, faces with two equivalent Se(3)Sm5 square pyramids, and  a faceface with one Se(2)Sm5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 18-49°. In the second Se site, Se(2) is bonded to one Sm(2), two equivalent Sm(1), and two equivalent Sm(3) atoms to form distorted SeSm5 trigonal bipyramids that share corners with five equivalent Se(1)Sm6 octahedra, corners with four equivalent Se(3)Sm5 square pyramids, corners with four equivalent Se(2)Sm5 trigonal bipyramids, edges with three equivalent Se(1)Sm6 octahedra, edges with four equivalent Se(3)Sm5 square pyramids,  an edgeedge with one Se(2)Sm5 trigonal bipyramid,  a faceface with one Se(1)Sm6 octahedra, and  a faceface with one Se(2)Sm5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 23-50°. In the third Se site, Se(3) is bonded to one Sm(2), one Sm(3), and three equivalent Sm(1) atoms to form distorted SeSm5 square pyramids that share corners with seven equivalent Se(1)Sm6 octahedra, corners with five equivalent Se(3)Sm5 square pyramids, corners with four equivalent Se(2)Sm5 trigonal bipyramids,  an edgeedge with one Se(1)Sm6 octahedra, edges with four equivalent Se(2)Sm5 trigonal bipyramids, faces with two equivalent Se(1)Sm6 octahedra, and  a faceface with one Se(3)Sm5 square pyramid. The corner-sharing octahedral tilt angles range from 14-54°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sm2Se3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.647
_cell_length_b   14.647
_cell_length_c   14.647
_cell_angle_alpha   144.888
_cell_angle_beta   144.888
_cell_angle_gamma   50.501
_symmetry_Int_Tables_number   1
_cell_volume   1034.299
_cell_formula_units_Z   8
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
  Sm  Sm0  1  0.846  0.952  0.376  1.0
  Sm  Sm1  1  0.575  0.470  0.624  1.0
  Sm  Sm2  1  0.166  0.166  1.000  1.0
  Sm  Sm3  1  0.875  0.506  0.131  1.0
  Sm  Sm4  1  0.175  0.298  0.395  1.0
  Sm  Sm5  1  0.584  0.084  0.500  1.0
  Sm  Sm6  1  0.904  0.780  0.605  1.0
  Sm  Sm7  1  0.375  0.744  0.869  1.0
  Sm  Sm8  1  0.220  0.825  0.123  1.0
  Sm  Sm9  1  0.916  0.416  0.500  1.0
  Sm  Sm10  1  0.494  0.625  0.369  1.0
  Sm  Sm11  1  0.256  0.125  0.631  1.0
  Sm  Sm12  1  0.702  0.096  0.876  1.0
  Sm  Sm13  1  0.834  0.834  0.000  1.0
  Sm  Sm14  1  0.530  0.154  0.106  1.0
  Sm  Sm15  1  0.048  0.425  0.894  1.0
  Se  Se16  1  0.506  0.115  0.254  1.0
  Se  Se17  1  0.074  0.827  0.611  1.0
  Se  Se18  1  0.862  0.252  0.746  1.0
  Se  Se19  1  0.888  0.135  0.891  1.0
  Se  Se20  1  0.244  0.998  0.109  1.0
  Se  Se21  1  0.676  0.787  0.253  1.0
  Se  Se22  1  0.216  0.463  0.389  1.0
  Se  Se23  1  0.842  0.438  0.246  1.0
  Se  Se24  1  0.534  0.423  0.747  1.0
  Se  Se25  1  0.404  0.158  0.596  1.0
  Se  Se26  1  0.192  0.596  0.754  1.0
  Se  Se27  1  0.213  0.466  0.889  1.0
  Se  Se28  1  0.577  0.324  0.111  1.0
  Se  Se29  1  0.002  0.112  0.246  1.0
  Se  Se30  1  0.562  0.808  0.404  1.0
  Se  Se31  1  0.173  0.784  0.246  1.0
  Se  Se32  1  0.865  0.756  0.754  1.0
  Se  Se33  1  0.748  0.494  0.609  1.0
  Se  Se34  1  0.537  0.926  0.754  1.0
  Se  Se35  1  0.558  0.812  0.904  1.0
  Se  Se36  1  0.908  0.654  0.096  1.0
  Se  Se37  1  0.346  0.442  0.254  1.0
  Se  Se38  1  0.885  0.138  0.391  1.0
  Se  Se39  1  0.188  0.092  0.746  1.0
[/CIF]
.