The crystal structure described by Tb3Si2O6Cl5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(1), one O(3), one Cl(1), one Cl(4), and three equivalent Cl(3) atoms to form distorted TbCl5O2 pentagonal bipyramids that share corners with four equivalent Tb(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Tb(2)Cl2O6 hexagonal bipyramid, and edges with two equivalent Tb(1)Cl5O2 pentagonal bipyramids. In the second Tb site, Tb(2) is bonded to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent Cl(2) atoms to form distorted TbCl2O6 hexagonal bipyramids that share corners with four equivalent Tb(2)Cl2O6 hexagonal bipyramids, edges with two equivalent Tb(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 Tb(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Tb(2)Cl2O6 hexagonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Tb(1), one Tb(2), and one Si(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Tb(1), one Tb(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Tb(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 Tb(1) atoms. In the second Cl site, Cl(2) is bonded in a bent 150 degrees geometry to two equivalent Tb(2) atoms. In the third Cl site, Cl(3) is bonded in a trigonal planar geometry to three equivalent Tb(1) atoms. In the fourth Cl site, Cl(4) is bonded in a bent 150 degrees geometry to two equivalent Tb(1) atoms. is represented by the CIF file [CIF]
data_Tb3Si2Cl5O6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.483
_cell_length_b   7.483
_cell_length_c   11.774
_cell_angle_alpha   80.623
_cell_angle_beta   80.623
_cell_angle_gamma   88.814
_symmetry_Int_Tables_number   1
_cell_volume   641.705
_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
  Tb  Tb0  1  0.416  0.918  0.330  1.0
  Tb  Tb1  1  0.584  0.082  0.670  1.0
  Tb  Tb2  1  0.000  0.500  0.000  1.0
  Tb  Tb3  1  0.918  0.416  0.330  1.0
  Tb  Tb4  1  0.500  0.000  0.000  1.0
  Tb  Tb5  1  0.082  0.584  0.670  1.0
  Si  Si6  1  0.182  0.890  0.856  1.0
  Si  Si7  1  0.818  0.110  0.144  1.0
  Si  Si8  1  0.890  0.182  0.856  1.0
  Si  Si9  1  0.110  0.818  0.144  1.0
  Cl  Cl10  1  0.219  0.219  0.339  1.0
  Cl  Cl11  1  0.314  0.314  0.998  1.0
  Cl  Cl12  1  0.781  0.781  0.661  1.0
  Cl  Cl13  1  0.673  0.116  0.421  1.0
  Cl  Cl14  1  0.381  0.381  0.646  1.0
  Cl  Cl15  1  0.327  0.884  0.579  1.0
  Cl  Cl16  1  0.116  0.673  0.421  1.0
  Cl  Cl17  1  0.686  0.686  0.002  1.0
  Cl  Cl18  1  0.619  0.619  0.354  1.0
  Cl  Cl19  1  0.884  0.327  0.579  1.0
  O  O20  1  0.307  0.869  0.172  1.0
  O  O21  1  0.693  0.131  0.828  1.0
  O  O22  1  0.131  0.693  0.828  1.0
  O  O23  1  0.952  0.952  0.193  1.0
  O  O24  1  0.956  0.393  0.828  1.0
  O  O25  1  0.869  0.307  0.172  1.0
  O  O26  1  0.393  0.956  0.828  1.0
  O  O27  1  0.144  0.856  0.000  1.0
  O  O28  1  0.044  0.607  0.172  1.0
  O  O29  1  0.607  0.044  0.172  1.0
  O  O30  1  0.048  0.048  0.807  1.0
  O  O31  1  0.856  0.144  0.000  1.0
[/CIF]
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The crystal structure described by Tb3Si2O6Cl5 crystallizes in the monoclinic C2/m space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(1), one O(3), one Cl(1), one Cl(4), and three equivalent Cl(3) atoms to form distorted TbCl5O2 pentagonal bipyramids that share corners with four equivalent Tb(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Tb(2)Cl2O6 hexagonal bipyramid, and edges with two equivalent Tb(1)Cl5O2 pentagonal bipyramids. In the second Tb site, Tb(2) is bonded to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent Cl(2) atoms to form distorted TbCl2O6 hexagonal bipyramids that share corners with four equivalent Tb(2)Cl2O6 hexagonal bipyramids, edges with two equivalent Tb(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 Tb(1)Cl5O2 pentagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Tb(2)Cl2O6 hexagonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Tb(1), one Tb(2), and one Si(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Tb(1), one Tb(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Tb(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 Tb(1) atoms. In the second Cl site, Cl(2) is bonded in a bent 150 degrees geometry to two equivalent Tb(2) atoms. In the third Cl site, Cl(3) is bonded in a trigonal planar geometry to three equivalent Tb(1) atoms. In the fourth Cl site, Cl(4) is bonded in a bent 150 degrees geometry to two equivalent Tb(1) atoms. is represented by the CIF file [CIF]
data_Tb3Si2Cl5O6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.483
_cell_length_b   7.483
_cell_length_c   11.774
_cell_angle_alpha   80.623
_cell_angle_beta   80.623
_cell_angle_gamma   88.814
_symmetry_Int_Tables_number   1
_cell_volume   641.705
_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
  Tb  Tb0  1  0.416  0.918  0.330  1.0
  Tb  Tb1  1  0.584  0.082  0.670  1.0
  Tb  Tb2  1  0.000  0.500  0.000  1.0
  Tb  Tb3  1  0.918  0.416  0.330  1.0
  Tb  Tb4  1  0.500  0.000  0.000  1.0
  Tb  Tb5  1  0.082  0.584  0.670  1.0
  Si  Si6  1  0.182  0.890  0.856  1.0
  Si  Si7  1  0.818  0.110  0.144  1.0
  Si  Si8  1  0.890  0.182  0.856  1.0
  Si  Si9  1  0.110  0.818  0.144  1.0
  Cl  Cl10  1  0.219  0.219  0.339  1.0
  Cl  Cl11  1  0.314  0.314  0.998  1.0
  Cl  Cl12  1  0.781  0.781  0.661  1.0
  Cl  Cl13  1  0.673  0.116  0.421  1.0
  Cl  Cl14  1  0.381  0.381  0.646  1.0
  Cl  Cl15  1  0.327  0.884  0.579  1.0
  Cl  Cl16  1  0.116  0.673  0.421  1.0
  Cl  Cl17  1  0.686  0.686  0.002  1.0
  Cl  Cl18  1  0.619  0.619  0.354  1.0
  Cl  Cl19  1  0.884  0.327  0.579  1.0
  O  O20  1  0.307  0.869  0.172  1.0
  O  O21  1  0.693  0.131  0.828  1.0
  O  O22  1  0.131  0.693  0.828  1.0
  O  O23  1  0.952  0.952  0.193  1.0
  O  O24  1  0.956  0.393  0.828  1.0
  O  O25  1  0.869  0.307  0.172  1.0
  O  O26  1  0.393  0.956  0.828  1.0
  O  O27  1  0.144  0.856  0.000  1.0
  O  O28  1  0.044  0.607  0.172  1.0
  O  O29  1  0.607  0.044  0.172  1.0
  O  O30  1  0.048  0.048  0.807  1.0
  O  O31  1  0.856  0.144  0.000  1.0
[/CIF]
.