The material described by Sm3Si2O6Cl5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(2), one O(3), one Cl(1), one Cl(3), and three equivalent Cl(2) atoms to form distorted SmCl5O2 pentagonal bipyramids that share corners with four equivalent Sm(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Sm(2)Cl2O6 hexagonal bipyramid, and edges with two equivalent Sm(1)Cl5O2 pentagonal bipyramids. In the second Sm site, Sm(2) is bonded to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent Cl(4) atoms to form distorted SmCl2O6 hexagonal bipyramids that share corners with four equivalent Sm(2)Cl2O6 hexagonal bipyramids, edges with two equivalent Sm(1)Cl5O2 pentagonal bipyramids, and edges with four equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Sm(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Sm(2)Cl2O6 hexagonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Sm(1), one Sm(2), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Sm(1), one Sm(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Sm(2) and two equivalent Si(1) atoms. There are four inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a bent 150 degrees geometry to two equivalent Sm(1) atoms. In the second Cl site, Cl(2) is bonded in a trigonal non-coplanar geometry to three equivalent Sm(1) atoms. In the third Cl site, Cl(3) is bonded in a bent 150 degrees geometry to two equivalent Sm(1) atoms. In the fourth Cl site, Cl(4) is bonded in a bent 150 degrees geometry to two equivalent Sm(2) atoms. is represented by the CIF file [CIF]
data_Sm3Si2Cl5O6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.557
_cell_length_b   7.557
_cell_length_c   11.994
_cell_angle_alpha   80.706
_cell_angle_beta   80.706
_cell_angle_gamma   89.347
_symmetry_Int_Tables_number   1
_cell_volume   667.096
_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  0.082  0.585  0.669  1.0
  Sm  Sm1  1  0.500  0.000  0.000  1.0
  Sm  Sm2  1  0.585  0.082  0.669  1.0
  Sm  Sm3  1  0.918  0.415  0.331  1.0
  Sm  Sm4  1  0.415  0.918  0.331  1.0
  Sm  Sm5  1  0.000  0.500  0.000  1.0
  Si  Si6  1  0.109  0.819  0.142  1.0
  Si  Si7  1  0.819  0.109  0.142  1.0
  Si  Si8  1  0.181  0.891  0.858  1.0
  Si  Si9  1  0.891  0.181  0.858  1.0
  Cl  Cl10  1  0.383  0.383  0.641  1.0
  Cl  Cl11  1  0.320  0.892  0.579  1.0
  Cl  Cl12  1  0.108  0.680  0.421  1.0
  Cl  Cl13  1  0.770  0.770  0.668  1.0
  Cl  Cl14  1  0.317  0.317  0.996  1.0
  Cl  Cl15  1  0.892  0.320  0.579  1.0
  Cl  Cl16  1  0.683  0.683  0.004  1.0
  Cl  Cl17  1  0.230  0.230  0.332  1.0
  Cl  Cl18  1  0.680  0.108  0.421  1.0
  Cl  Cl19  1  0.617  0.617  0.359  1.0
  O  O20  1  0.953  0.953  0.187  1.0
  O  O21  1  0.042  0.611  0.172  1.0
  O  O22  1  0.389  0.958  0.828  1.0
  O  O23  1  0.130  0.698  0.828  1.0
  O  O24  1  0.870  0.302  0.172  1.0
  O  O25  1  0.302  0.870  0.172  1.0
  O  O26  1  0.853  0.147  0.000  1.0
  O  O27  1  0.698  0.130  0.828  1.0
  O  O28  1  0.147  0.853  0.000  1.0
  O  O29  1  0.611  0.042  0.172  1.0
  O  O30  1  0.958  0.389  0.828  1.0
  O  O31  1  0.047  0.047  0.813  1.0
[/CIF]
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The material described by Sm3Si2O6Cl5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(2), one O(3), one Cl(1), one Cl(3), and three equivalent Cl(2) atoms to form distorted SmCl5O2 pentagonal bipyramids that share corners with four equivalent Sm(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Sm(2)Cl2O6 hexagonal bipyramid, and edges with two equivalent Sm(1)Cl5O2 pentagonal bipyramids. In the second Sm site, Sm(2) is bonded to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent Cl(4) atoms to form distorted SmCl2O6 hexagonal bipyramids that share corners with four equivalent Sm(2)Cl2O6 hexagonal bipyramids, edges with two equivalent Sm(1)Cl5O2 pentagonal bipyramids, and edges with four equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Sm(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Sm(2)Cl2O6 hexagonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Sm(1), one Sm(2), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Sm(1), one Sm(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Sm(2) and two equivalent Si(1) atoms. There are four inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a bent 150 degrees geometry to two equivalent Sm(1) atoms. In the second Cl site, Cl(2) is bonded in a trigonal non-coplanar geometry to three equivalent Sm(1) atoms. In the third Cl site, Cl(3) is bonded in a bent 150 degrees geometry to two equivalent Sm(1) atoms. In the fourth Cl site, Cl(4) is bonded in a bent 150 degrees geometry to two equivalent Sm(2) atoms. is represented by the CIF file [CIF]
data_Sm3Si2Cl5O6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.557
_cell_length_b   7.557
_cell_length_c   11.994
_cell_angle_alpha   80.706
_cell_angle_beta   80.706
_cell_angle_gamma   89.347
_symmetry_Int_Tables_number   1
_cell_volume   667.096
_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  0.082  0.585  0.669  1.0
  Sm  Sm1  1  0.500  0.000  0.000  1.0
  Sm  Sm2  1  0.585  0.082  0.669  1.0
  Sm  Sm3  1  0.918  0.415  0.331  1.0
  Sm  Sm4  1  0.415  0.918  0.331  1.0
  Sm  Sm5  1  0.000  0.500  0.000  1.0
  Si  Si6  1  0.109  0.819  0.142  1.0
  Si  Si7  1  0.819  0.109  0.142  1.0
  Si  Si8  1  0.181  0.891  0.858  1.0
  Si  Si9  1  0.891  0.181  0.858  1.0
  Cl  Cl10  1  0.383  0.383  0.641  1.0
  Cl  Cl11  1  0.320  0.892  0.579  1.0
  Cl  Cl12  1  0.108  0.680  0.421  1.0
  Cl  Cl13  1  0.770  0.770  0.668  1.0
  Cl  Cl14  1  0.317  0.317  0.996  1.0
  Cl  Cl15  1  0.892  0.320  0.579  1.0
  Cl  Cl16  1  0.683  0.683  0.004  1.0
  Cl  Cl17  1  0.230  0.230  0.332  1.0
  Cl  Cl18  1  0.680  0.108  0.421  1.0
  Cl  Cl19  1  0.617  0.617  0.359  1.0
  O  O20  1  0.953  0.953  0.187  1.0
  O  O21  1  0.042  0.611  0.172  1.0
  O  O22  1  0.389  0.958  0.828  1.0
  O  O23  1  0.130  0.698  0.828  1.0
  O  O24  1  0.870  0.302  0.172  1.0
  O  O25  1  0.302  0.870  0.172  1.0
  O  O26  1  0.853  0.147  0.000  1.0
  O  O27  1  0.698  0.130  0.828  1.0
  O  O28  1  0.147  0.853  0.000  1.0
  O  O29  1  0.611  0.042  0.172  1.0
  O  O30  1  0.958  0.389  0.828  1.0
  O  O31  1  0.047  0.047  0.813  1.0
[/CIF]
.