The compound described by K8Sn8Se20O9 crystallizes in the trigonal R3 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 3-coordinate geometry to three equivalent Se(3) and three equivalent O(3) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to three equivalent Se(4) and three equivalent O(3) atoms. In the third K site, K(3) is bonded in a 2-coordinate geometry to one Se(2), one Se(4), one Se(7), one O(1), and one O(2) atom. In the fourth K site, K(4) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(8), one O(1), and one O(2) atom. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form a mixture of corner and edge-sharing SnSe4 tetrahedra. In the second Sn site, Sn(2) is bonded to one Se(2), one Se(3), one Se(4), and one Se(6) atom to form a mixture of corner and edge-sharing SnSe4 tetrahedra. In the third Sn site, Sn(3) is bonded to one Se(7) and three equivalent Se(1) atoms to form corner-sharing SnSe4 tetrahedra. In the fourth Sn site, Sn(4) is bonded to one Se(8) and three equivalent Se(2) atoms to form corner-sharing SnSe4 tetrahedra. There are eight inequivalent Se sites. In the first Se site, Se(1) is bonded in a 3-coordinate geometry to one K(4), one Sn(1), and one Sn(3) atom. In the second Se site, Se(2) is bonded to one K(3), one K(4), one Sn(2), and one Sn(4) atom to form distorted corner-sharing SeK2Sn2 trigonal pyramids. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one K(1), one K(4), one Sn(1), and one Sn(2) atom. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to one K(2), one K(3), one Sn(1), and one Sn(2) atom. In the fifth Se site, Se(5) is bonded in a distorted water-like geometry to one Sn(1), one O(2), and one O(3) atom. In the sixth Se site, Se(6) is bonded in a distorted water-like geometry to one Sn(2) and one O(1) atom. In the seventh Se site, Se(7) is bonded in a 5-coordinate geometry to three equivalent K(3), one Sn(3), and one Se(8) atom. In the eighth Se site, Se(8) is bonded in a 5-coordinate geometry to three equivalent K(4), one Sn(4), and one Se(7) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one K(3), one K(4), and one Se(6) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(3), one K(4), and one Se(5) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one K(1), one K(2), and one Se(5) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_K8Sn8Se20O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.211
_cell_length_b   11.211
_cell_length_c   11.211
_cell_angle_alpha   85.942
_cell_angle_beta   85.942
_cell_angle_gamma   85.942
_symmetry_Int_Tables_number   1
_cell_volume   1398.897
_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
  K  K0  1  0.104  0.104  0.104  1.0
  K  K1  1  0.916  0.916  0.916  1.0
  K  K2  1  0.621  0.207  0.520  1.0
  K  K3  1  0.520  0.621  0.207  1.0
  K  K4  1  0.207  0.520  0.621  1.0
  K  K5  1  0.391  0.803  0.487  1.0
  K  K6  1  0.487  0.391  0.803  1.0
  K  K7  1  0.803  0.487  0.391  1.0
  Sn  Sn8  1  0.086  0.119  0.534  1.0
  Sn  Sn9  1  0.534  0.086  0.119  1.0
  Sn  Sn10  1  0.119  0.534  0.086  1.0
  Sn  Sn11  1  0.899  0.882  0.461  1.0
  Sn  Sn12  1  0.461  0.899  0.882  1.0
  Sn  Sn13  1  0.882  0.461  0.899  1.0
  Sn  Sn14  1  0.310  0.310  0.310  1.0
  Sn  Sn15  1  0.687  0.687  0.687  1.0
  Se  Se16  1  0.083  0.315  0.386  1.0
  Se  Se17  1  0.386  0.083  0.315  1.0
  Se  Se18  1  0.315  0.386  0.083  1.0
  Se  Se19  1  0.912  0.686  0.604  1.0
  Se  Se20  1  0.604  0.912  0.686  1.0
  Se  Se21  1  0.686  0.604  0.912  1.0
  Se  Se22  1  0.119  0.937  0.393  1.0
  Se  Se23  1  0.393  0.119  0.937  1.0
  Se  Se24  1  0.937  0.393  0.119  1.0
  Se  Se25  1  0.871  0.058  0.608  1.0
  Se  Se26  1  0.608  0.871  0.058  1.0
  Se  Se27  1  0.058  0.608  0.871  1.0
  Se  Se28  1  0.207  0.157  0.750  1.0
  Se  Se29  1  0.750  0.207  0.157  1.0
  Se  Se30  1  0.157  0.750  0.207  1.0
  Se  Se31  1  0.775  0.838  0.276  1.0
  Se  Se32  1  0.276  0.775  0.838  1.0
  Se  Se33  1  0.838  0.276  0.775  1.0
  Se  Se34  1  0.429  0.429  0.429  1.0
  Se  Se35  1  0.568  0.568  0.568  1.0
  O  O36  1  0.309  0.719  0.698  1.0
  O  O37  1  0.698  0.309  0.719  1.0
  O  O38  1  0.719  0.698  0.309  1.0
  O  O39  1  0.713  0.247  0.298  1.0
  O  O40  1  0.298  0.713  0.247  1.0
  O  O41  1  0.247  0.298  0.713  1.0
  O  O42  1  0.848  0.084  0.156  1.0
  O  O43  1  0.156  0.848  0.084  1.0
  O  O44  1  0.084  0.156  0.848  1.0
[/CIF]
.
The compound described by K8Sn8Se20O9 crystallizes in the trigonal R3 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 3-coordinate geometry to three equivalent Se(3) and three equivalent O(3) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to three equivalent Se(4) and three equivalent O(3) atoms. In the third K site, K(3) is bonded in a 2-coordinate geometry to one Se(2), one Se(4), one Se(7), one O(1), and one O(2) atom. In the fourth K site, K(4) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(8), one O(1), and one O(2) atom. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form a mixture of corner and edge-sharing SnSe4 tetrahedra. In the second Sn site, Sn(2) is bonded to one Se(2), one Se(3), one Se(4), and one Se(6) atom to form a mixture of corner and edge-sharing SnSe4 tetrahedra. In the third Sn site, Sn(3) is bonded to one Se(7) and three equivalent Se(1) atoms to form corner-sharing SnSe4 tetrahedra. In the fourth Sn site, Sn(4) is bonded to one Se(8) and three equivalent Se(2) atoms to form corner-sharing SnSe4 tetrahedra. There are eight inequivalent Se sites. In the first Se site, Se(1) is bonded in a 3-coordinate geometry to one K(4), one Sn(1), and one Sn(3) atom. In the second Se site, Se(2) is bonded to one K(3), one K(4), one Sn(2), and one Sn(4) atom to form distorted corner-sharing SeK2Sn2 trigonal pyramids. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one K(1), one K(4), one Sn(1), and one Sn(2) atom. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to one K(2), one K(3), one Sn(1), and one Sn(2) atom. In the fifth Se site, Se(5) is bonded in a distorted water-like geometry to one Sn(1), one O(2), and one O(3) atom. In the sixth Se site, Se(6) is bonded in a distorted water-like geometry to one Sn(2) and one O(1) atom. In the seventh Se site, Se(7) is bonded in a 5-coordinate geometry to three equivalent K(3), one Sn(3), and one Se(8) atom. In the eighth Se site, Se(8) is bonded in a 5-coordinate geometry to three equivalent K(4), one Sn(4), and one Se(7) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one K(3), one K(4), and one Se(6) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(3), one K(4), and one Se(5) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one K(1), one K(2), and one Se(5) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_K8Sn8Se20O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.211
_cell_length_b   11.211
_cell_length_c   11.211
_cell_angle_alpha   85.942
_cell_angle_beta   85.942
_cell_angle_gamma   85.942
_symmetry_Int_Tables_number   1
_cell_volume   1398.897
_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
  K  K0  1  0.104  0.104  0.104  1.0
  K  K1  1  0.916  0.916  0.916  1.0
  K  K2  1  0.621  0.207  0.520  1.0
  K  K3  1  0.520  0.621  0.207  1.0
  K  K4  1  0.207  0.520  0.621  1.0
  K  K5  1  0.391  0.803  0.487  1.0
  K  K6  1  0.487  0.391  0.803  1.0
  K  K7  1  0.803  0.487  0.391  1.0
  Sn  Sn8  1  0.086  0.119  0.534  1.0
  Sn  Sn9  1  0.534  0.086  0.119  1.0
  Sn  Sn10  1  0.119  0.534  0.086  1.0
  Sn  Sn11  1  0.899  0.882  0.461  1.0
  Sn  Sn12  1  0.461  0.899  0.882  1.0
  Sn  Sn13  1  0.882  0.461  0.899  1.0
  Sn  Sn14  1  0.310  0.310  0.310  1.0
  Sn  Sn15  1  0.687  0.687  0.687  1.0
  Se  Se16  1  0.083  0.315  0.386  1.0
  Se  Se17  1  0.386  0.083  0.315  1.0
  Se  Se18  1  0.315  0.386  0.083  1.0
  Se  Se19  1  0.912  0.686  0.604  1.0
  Se  Se20  1  0.604  0.912  0.686  1.0
  Se  Se21  1  0.686  0.604  0.912  1.0
  Se  Se22  1  0.119  0.937  0.393  1.0
  Se  Se23  1  0.393  0.119  0.937  1.0
  Se  Se24  1  0.937  0.393  0.119  1.0
  Se  Se25  1  0.871  0.058  0.608  1.0
  Se  Se26  1  0.608  0.871  0.058  1.0
  Se  Se27  1  0.058  0.608  0.871  1.0
  Se  Se28  1  0.207  0.157  0.750  1.0
  Se  Se29  1  0.750  0.207  0.157  1.0
  Se  Se30  1  0.157  0.750  0.207  1.0
  Se  Se31  1  0.775  0.838  0.276  1.0
  Se  Se32  1  0.276  0.775  0.838  1.0
  Se  Se33  1  0.838  0.276  0.775  1.0
  Se  Se34  1  0.429  0.429  0.429  1.0
  Se  Se35  1  0.568  0.568  0.568  1.0
  O  O36  1  0.309  0.719  0.698  1.0
  O  O37  1  0.698  0.309  0.719  1.0
  O  O38  1  0.719  0.698  0.309  1.0
  O  O39  1  0.713  0.247  0.298  1.0
  O  O40  1  0.298  0.713  0.247  1.0
  O  O41  1  0.247  0.298  0.713  1.0
  O  O42  1  0.848  0.084  0.156  1.0
  O  O43  1  0.156  0.848  0.084  1.0
  O  O44  1  0.084  0.156  0.848  1.0
[/CIF]
.