The structure described by Er3SmSe6 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded to one Se(5), two equivalent Se(1), and three equivalent Se(2) atoms to form ErSe6 octahedra that share corners with three equivalent Er(3)Se6 octahedra, corners with two equivalent Er(2)Se7 pentagonal bipyramids, and edges with four equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. In the second Er site, Er(2) is bonded to one Se(1), one Se(6), two equivalent Se(3), and three equivalent Se(4) atoms to form distorted ErSe7 pentagonal bipyramids that share  a cornercorner with one Er(3)Se6 octahedra, corners with two equivalent Er(1)Se6 octahedra, edges with two equivalent Er(3)Se6 octahedra, and edges with four equivalent Er(2)Se7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 37-50°. In the third Er site, Er(3) is bonded to one Se(4), two equivalent Se(6), and three equivalent Se(5) atoms to form ErSe6 octahedra that share corners with three equivalent Er(1)Se6 octahedra,  a cornercorner with one Er(2)Se7 pentagonal bipyramid, edges with four equivalent Er(3)Se6 octahedra, and edges with two equivalent Er(2)Se7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 56-60°. Sm(1) is bonded in a 8-coordinate geometry to one Se(1), two equivalent Se(2), two equivalent Se(6), and three equivalent Se(3) atoms. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one Er(2), two equivalent Er(1), and one Sm(1) atom to form distorted SeSmEr3 trigonal pyramids that share corners with two equivalent Se(2)Sm2Er3 square pyramids,  a cornercorner with one Se(3)Sm3Er2 trigonal bipyramid, corners with three equivalent Se(6)Sm2Er3 trigonal bipyramids, corners with two equivalent Se(1)SmEr3 trigonal pyramids, corners with three equivalent Se(4)Er4 trigonal pyramids, edges with three equivalent Se(2)Sm2Er3 square pyramids, and edges with two equivalent Se(3)Sm3Er2 trigonal bipyramids. In the second Se site, Se(2) is bonded to three equivalent Er(1) and two equivalent Sm(1) atoms to form SeSm2Er3 square pyramids that share corners with two equivalent Se(6)Sm2Er3 trigonal bipyramids, corners with four equivalent Se(3)Sm3Er2 trigonal bipyramids, corners with two equivalent Se(1)SmEr3 trigonal pyramids, edges with four equivalent Se(2)Sm2Er3 square pyramids,  an edgeedge with one Se(6)Sm2Er3 trigonal bipyramid,  an edgeedge with one Se(3)Sm3Er2 trigonal bipyramid, and edges with three equivalent Se(1)SmEr3 trigonal pyramids. In the third Se site, Se(3) is bonded to two equivalent Er(2) and three equivalent Sm(1) atoms to form distorted SeSm3Er2 trigonal bipyramids that share corners with four equivalent Se(2)Sm2Er3 square pyramids, corners with two equivalent Se(6)Sm2Er3 trigonal bipyramids,  a cornercorner with one Se(1)SmEr3 trigonal pyramid, corners with four equivalent Se(4)Er4 trigonal pyramids,  an edgeedge with one Se(2)Sm2Er3 square pyramid, edges with three equivalent Se(6)Sm2Er3 trigonal bipyramids, edges with four equivalent Se(3)Sm3Er2 trigonal bipyramids,  an edgeedge with one Se(4)Er4 trigonal pyramid, and edges with two equivalent Se(1)SmEr3 trigonal pyramids. In the fourth Se site, Se(4) is bonded to one Er(3) and three equivalent Er(2) atoms to form distorted SeEr4 trigonal pyramids that share  a cornercorner with one Se(6)Sm2Er3 trigonal bipyramid, corners with four equivalent Se(3)Sm3Er2 trigonal bipyramids, corners with two equivalent Se(4)Er4 trigonal pyramids, corners with three equivalent Se(1)SmEr3 trigonal pyramids,  an edgeedge with one Se(3)Sm3Er2 trigonal bipyramid, edges with two equivalent Se(6)Sm2Er3 trigonal bipyramids, and edges with two equivalent Se(4)Er4 trigonal pyramids. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Er(1) and three equivalent Er(3) atoms. In the sixth Se site, Se(6) is bonded to one Er(2), two equivalent Er(3), and two equivalent Sm(1) atoms to form SeSm2Er3 trigonal bipyramids that share corners with two equivalent Se(2)Sm2Er3 square pyramids, corners with two equivalent Se(3)Sm3Er2 trigonal bipyramids,  a cornercorner with one Se(4)Er4 trigonal pyramid, corners with three equivalent Se(1)SmEr3 trigonal pyramids,  an edgeedge with one Se(2)Sm2Er3 square pyramid, edges with two equivalent Se(6)Sm2Er3 trigonal bipyramids, edges with three equivalent Se(3)Sm3Er2 trigonal bipyramids, and edges with two equivalent Se(4)Er4 trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sm(ErSe2)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.082
_cell_length_b   11.496
_cell_length_c   11.761
_cell_angle_alpha   70.799
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   521.198
_cell_formula_units_Z   2
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  0.250  0.454  0.195  1.0
  Sm  Sm1  1  0.750  0.546  0.805  1.0
  Er  Er2  1  0.250  0.340  0.586  1.0
  Er  Er3  1  0.750  0.660  0.414  1.0
  Er  Er4  1  0.250  0.818  0.001  1.0
  Er  Er5  1  0.750  0.182  0.999  1.0
  Er  Er6  1  0.250  0.063  0.333  1.0
  Er  Er7  1  0.750  0.937  0.667  1.0
  Se  Se8  1  0.250  0.697  0.250  1.0
  Se  Se9  1  0.750  0.303  0.750  1.0
  Se  Se10  1  0.250  0.582  0.595  1.0
  Se  Se11  1  0.750  0.418  0.405  1.0
  Se  Se12  1  0.250  0.385  0.965  1.0
  Se  Se13  1  0.750  0.615  0.035  1.0
  Se  Se14  1  0.250  0.021  0.114  1.0
  Se  Se15  1  0.750  0.979  0.886  1.0
  Se  Se16  1  0.750  0.894  0.440  1.0
  Se  Se17  1  0.250  0.106  0.560  1.0
  Se  Se18  1  0.750  0.240  0.226  1.0
  Se  Se19  1  0.250  0.760  0.774  1.0
[/CIF]
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The structure described by Er3SmSe6 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded to one Se(5), two equivalent Se(1), and three equivalent Se(2) atoms to form ErSe6 octahedra that share corners with three equivalent Er(3)Se6 octahedra, corners with two equivalent Er(2)Se7 pentagonal bipyramids, and edges with four equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. In the second Er site, Er(2) is bonded to one Se(1), one Se(6), two equivalent Se(3), and three equivalent Se(4) atoms to form distorted ErSe7 pentagonal bipyramids that share  a cornercorner with one Er(3)Se6 octahedra, corners with two equivalent Er(1)Se6 octahedra, edges with two equivalent Er(3)Se6 octahedra, and edges with four equivalent Er(2)Se7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 37-50°. In the third Er site, Er(3) is bonded to one Se(4), two equivalent Se(6), and three equivalent Se(5) atoms to form ErSe6 octahedra that share corners with three equivalent Er(1)Se6 octahedra,  a cornercorner with one Er(2)Se7 pentagonal bipyramid, edges with four equivalent Er(3)Se6 octahedra, and edges with two equivalent Er(2)Se7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 56-60°. Sm(1) is bonded in a 8-coordinate geometry to one Se(1), two equivalent Se(2), two equivalent Se(6), and three equivalent Se(3) atoms. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one Er(2), two equivalent Er(1), and one Sm(1) atom to form distorted SeSmEr3 trigonal pyramids that share corners with two equivalent Se(2)Sm2Er3 square pyramids,  a cornercorner with one Se(3)Sm3Er2 trigonal bipyramid, corners with three equivalent Se(6)Sm2Er3 trigonal bipyramids, corners with two equivalent Se(1)SmEr3 trigonal pyramids, corners with three equivalent Se(4)Er4 trigonal pyramids, edges with three equivalent Se(2)Sm2Er3 square pyramids, and edges with two equivalent Se(3)Sm3Er2 trigonal bipyramids. In the second Se site, Se(2) is bonded to three equivalent Er(1) and two equivalent Sm(1) atoms to form SeSm2Er3 square pyramids that share corners with two equivalent Se(6)Sm2Er3 trigonal bipyramids, corners with four equivalent Se(3)Sm3Er2 trigonal bipyramids, corners with two equivalent Se(1)SmEr3 trigonal pyramids, edges with four equivalent Se(2)Sm2Er3 square pyramids,  an edgeedge with one Se(6)Sm2Er3 trigonal bipyramid,  an edgeedge with one Se(3)Sm3Er2 trigonal bipyramid, and edges with three equivalent Se(1)SmEr3 trigonal pyramids. In the third Se site, Se(3) is bonded to two equivalent Er(2) and three equivalent Sm(1) atoms to form distorted SeSm3Er2 trigonal bipyramids that share corners with four equivalent Se(2)Sm2Er3 square pyramids, corners with two equivalent Se(6)Sm2Er3 trigonal bipyramids,  a cornercorner with one Se(1)SmEr3 trigonal pyramid, corners with four equivalent Se(4)Er4 trigonal pyramids,  an edgeedge with one Se(2)Sm2Er3 square pyramid, edges with three equivalent Se(6)Sm2Er3 trigonal bipyramids, edges with four equivalent Se(3)Sm3Er2 trigonal bipyramids,  an edgeedge with one Se(4)Er4 trigonal pyramid, and edges with two equivalent Se(1)SmEr3 trigonal pyramids. In the fourth Se site, Se(4) is bonded to one Er(3) and three equivalent Er(2) atoms to form distorted SeEr4 trigonal pyramids that share  a cornercorner with one Se(6)Sm2Er3 trigonal bipyramid, corners with four equivalent Se(3)Sm3Er2 trigonal bipyramids, corners with two equivalent Se(4)Er4 trigonal pyramids, corners with three equivalent Se(1)SmEr3 trigonal pyramids,  an edgeedge with one Se(3)Sm3Er2 trigonal bipyramid, edges with two equivalent Se(6)Sm2Er3 trigonal bipyramids, and edges with two equivalent Se(4)Er4 trigonal pyramids. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Er(1) and three equivalent Er(3) atoms. In the sixth Se site, Se(6) is bonded to one Er(2), two equivalent Er(3), and two equivalent Sm(1) atoms to form SeSm2Er3 trigonal bipyramids that share corners with two equivalent Se(2)Sm2Er3 square pyramids, corners with two equivalent Se(3)Sm3Er2 trigonal bipyramids,  a cornercorner with one Se(4)Er4 trigonal pyramid, corners with three equivalent Se(1)SmEr3 trigonal pyramids,  an edgeedge with one Se(2)Sm2Er3 square pyramid, edges with two equivalent Se(6)Sm2Er3 trigonal bipyramids, edges with three equivalent Se(3)Sm3Er2 trigonal bipyramids, and edges with two equivalent Se(4)Er4 trigonal pyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Sm(ErSe2)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.082
_cell_length_b   11.496
_cell_length_c   11.761
_cell_angle_alpha   70.799
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   521.198
_cell_formula_units_Z   2
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  0.250  0.454  0.195  1.0
  Sm  Sm1  1  0.750  0.546  0.805  1.0
  Er  Er2  1  0.250  0.340  0.586  1.0
  Er  Er3  1  0.750  0.660  0.414  1.0
  Er  Er4  1  0.250  0.818  0.001  1.0
  Er  Er5  1  0.750  0.182  0.999  1.0
  Er  Er6  1  0.250  0.063  0.333  1.0
  Er  Er7  1  0.750  0.937  0.667  1.0
  Se  Se8  1  0.250  0.697  0.250  1.0
  Se  Se9  1  0.750  0.303  0.750  1.0
  Se  Se10  1  0.250  0.582  0.595  1.0
  Se  Se11  1  0.750  0.418  0.405  1.0
  Se  Se12  1  0.250  0.385  0.965  1.0
  Se  Se13  1  0.750  0.615  0.035  1.0
  Se  Se14  1  0.250  0.021  0.114  1.0
  Se  Se15  1  0.750  0.979  0.886  1.0
  Se  Se16  1  0.750  0.894  0.440  1.0
  Se  Se17  1  0.250  0.106  0.560  1.0
  Se  Se18  1  0.750  0.240  0.226  1.0
  Se  Se19  1  0.250  0.760  0.774  1.0
[/CIF]
.