The crystal structure described by K2SnSe3 crystallizes in the triclinic P-1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to one Se(2), two equivalent Se(1), and three equivalent Se(3) atoms to form distorted KSe6 octahedra that share corners with two equivalent K(1)Se6 octahedra, corners with three equivalent K(2)Se6 octahedra, corners with three equivalent Sn(1)Se4 tetrahedra, edges with three equivalent K(1)Se6 octahedra, edges with five equivalent K(2)Se6 octahedra, and edges with two equivalent Sn(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-69°. In the second K site, K(2) is bonded to one Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form distorted KSe6 octahedra that share corners with two equivalent K(2)Se6 octahedra, corners with three equivalent K(1)Se6 octahedra, corners with five equivalent Sn(1)Se4 tetrahedra, edges with three equivalent K(2)Se6 octahedra, edges with five equivalent K(1)Se6 octahedra, and  an edgeedge with one Sn(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 12-69°. Sn(1) is bonded to one Se(1), one Se(3), and two equivalent Se(2) atoms to form distorted SnSe4 tetrahedra that share corners with three equivalent K(1)Se6 octahedra, corners with five equivalent K(2)Se6 octahedra,  an edgeedge with one K(2)Se6 octahedra, edges with two equivalent K(1)Se6 octahedra, and  an edgeedge with one Sn(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-91°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1), three equivalent K(2), and one Sn(1) atom to form a mixture of distorted corner and edge-sharing SeK5Sn octahedra. The corner-sharing octahedral tilt angles range from 3-59°. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one K(1), one K(2), and two equivalent Sn(1) atoms. In the third Se site, Se(3) is bonded to two equivalent K(2), three equivalent K(1), and one Sn(1) atom to form a mixture of corner and edge-sharing SeK5Sn octahedra. The corner-sharing octahedral tilt angles range from 3-59°. is represented by the Crystallographic Information File (CIF) [CIF]
data_K2SnSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.928
_cell_length_b   7.636
_cell_length_c   8.720
_cell_angle_alpha   76.225
_cell_angle_beta   75.237
_cell_angle_gamma   67.677
_symmetry_Int_Tables_number   1
_cell_volume   407.483
_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
  K  K0  1  0.387  0.791  0.896  1.0
  K  K1  1  0.613  0.209  0.104  1.0
  K  K2  1  0.145  0.467  0.686  1.0
  K  K3  1  0.855  0.533  0.314  1.0
  Sn  Sn4  1  0.849  0.063  0.689  1.0
  Sn  Sn5  1  0.151  0.937  0.311  1.0
  Se  Se6  1  0.653  0.405  0.715  1.0
  Se  Se7  1  0.769  0.955  0.454  1.0
  Se  Se8  1  0.860  0.808  0.927  1.0
  Se  Se9  1  0.347  0.595  0.285  1.0
  Se  Se10  1  0.140  0.192  0.073  1.0
  Se  Se11  1  0.231  0.045  0.546  1.0
[/CIF]
.
The crystal structure described by K2SnSe3 crystallizes in the triclinic P-1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to one Se(2), two equivalent Se(1), and three equivalent Se(3) atoms to form distorted KSe6 octahedra that share corners with two equivalent K(1)Se6 octahedra, corners with three equivalent K(2)Se6 octahedra, corners with three equivalent Sn(1)Se4 tetrahedra, edges with three equivalent K(1)Se6 octahedra, edges with five equivalent K(2)Se6 octahedra, and edges with two equivalent Sn(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-69°. In the second K site, K(2) is bonded to one Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form distorted KSe6 octahedra that share corners with two equivalent K(2)Se6 octahedra, corners with three equivalent K(1)Se6 octahedra, corners with five equivalent Sn(1)Se4 tetrahedra, edges with three equivalent K(2)Se6 octahedra, edges with five equivalent K(1)Se6 octahedra, and  an edgeedge with one Sn(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 12-69°. Sn(1) is bonded to one Se(1), one Se(3), and two equivalent Se(2) atoms to form distorted SnSe4 tetrahedra that share corners with three equivalent K(1)Se6 octahedra, corners with five equivalent K(2)Se6 octahedra,  an edgeedge with one K(2)Se6 octahedra, edges with two equivalent K(1)Se6 octahedra, and  an edgeedge with one Sn(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-91°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1), three equivalent K(2), and one Sn(1) atom to form a mixture of distorted corner and edge-sharing SeK5Sn octahedra. The corner-sharing octahedral tilt angles range from 3-59°. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one K(1), one K(2), and two equivalent Sn(1) atoms. In the third Se site, Se(3) is bonded to two equivalent K(2), three equivalent K(1), and one Sn(1) atom to form a mixture of corner and edge-sharing SeK5Sn octahedra. The corner-sharing octahedral tilt angles range from 3-59°. is represented by the Crystallographic Information File (CIF) [CIF]
data_K2SnSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.928
_cell_length_b   7.636
_cell_length_c   8.720
_cell_angle_alpha   76.225
_cell_angle_beta   75.237
_cell_angle_gamma   67.677
_symmetry_Int_Tables_number   1
_cell_volume   407.483
_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
  K  K0  1  0.387  0.791  0.896  1.0
  K  K1  1  0.613  0.209  0.104  1.0
  K  K2  1  0.145  0.467  0.686  1.0
  K  K3  1  0.855  0.533  0.314  1.0
  Sn  Sn4  1  0.849  0.063  0.689  1.0
  Sn  Sn5  1  0.151  0.937  0.311  1.0
  Se  Se6  1  0.653  0.405  0.715  1.0
  Se  Se7  1  0.769  0.955  0.454  1.0
  Se  Se8  1  0.860  0.808  0.927  1.0
  Se  Se9  1  0.347  0.595  0.285  1.0
  Se  Se10  1  0.140  0.192  0.073  1.0
  Se  Se11  1  0.231  0.045  0.546  1.0
[/CIF]
.