The material structure described by K2Se2O7 crystallizes in the monoclinic C2/c space group. K(1) is bonded in a 8-coordinate geometry to two equivalent O(3), three equivalent O(1), and three equivalent O(2) atoms. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing SeO4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to three equivalent K(1) and one Se(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent K(1) and one Se(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent K(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Se(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_K2Se2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.441
_cell_length_b   7.441
_cell_length_c   7.490
_cell_angle_alpha   87.064
_cell_angle_beta   87.064
_cell_angle_gamma   60.897
_symmetry_Int_Tables_number   1
_cell_volume   361.710
_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  0.794  0.499  0.635  1.0
  K  K1  1  0.501  0.206  0.865  1.0
  K  K2  1  0.206  0.501  0.365  1.0
  K  K3  1  0.499  0.794  0.135  1.0
  Se  Se4  1  0.285  0.927  0.629  1.0
  Se  Se5  1  0.073  0.715  0.871  1.0
  Se  Se6  1  0.715  0.073  0.371  1.0
  Se  Se7  1  0.927  0.285  0.129  1.0
  O  O8  1  0.354  0.755  0.476  1.0
  O  O9  1  0.245  0.646  0.024  1.0
  O  O10  1  0.646  0.245  0.524  1.0
  O  O11  1  0.755  0.354  0.976  1.0
  O  O12  1  0.465  0.859  0.774  1.0
  O  O13  1  0.141  0.535  0.726  1.0
  O  O14  1  0.535  0.141  0.226  1.0
  O  O15  1  0.859  0.465  0.274  1.0
  O  O16  1  0.187  0.164  0.557  1.0
  O  O17  1  0.836  0.813  0.943  1.0
  O  O18  1  0.813  0.836  0.443  1.0
  O  O19  1  0.164  0.187  0.057  1.0
  O  O20  1  0.065  0.935  0.750  1.0
  O  O21  1  0.935  0.065  0.250  1.0
[/CIF]
.
The material structure described by K2Se2O7 crystallizes in the monoclinic C2/c space group. K(1) is bonded in a 8-coordinate geometry to two equivalent O(3), three equivalent O(1), and three equivalent O(2) atoms. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing SeO4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to three equivalent K(1) and one Se(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent K(1) and one Se(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent K(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Se(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_K2Se2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.441
_cell_length_b   7.441
_cell_length_c   7.490
_cell_angle_alpha   87.064
_cell_angle_beta   87.064
_cell_angle_gamma   60.897
_symmetry_Int_Tables_number   1
_cell_volume   361.710
_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  0.794  0.499  0.635  1.0
  K  K1  1  0.501  0.206  0.865  1.0
  K  K2  1  0.206  0.501  0.365  1.0
  K  K3  1  0.499  0.794  0.135  1.0
  Se  Se4  1  0.285  0.927  0.629  1.0
  Se  Se5  1  0.073  0.715  0.871  1.0
  Se  Se6  1  0.715  0.073  0.371  1.0
  Se  Se7  1  0.927  0.285  0.129  1.0
  O  O8  1  0.354  0.755  0.476  1.0
  O  O9  1  0.245  0.646  0.024  1.0
  O  O10  1  0.646  0.245  0.524  1.0
  O  O11  1  0.755  0.354  0.976  1.0
  O  O12  1  0.465  0.859  0.774  1.0
  O  O13  1  0.141  0.535  0.726  1.0
  O  O14  1  0.535  0.141  0.226  1.0
  O  O15  1  0.859  0.465  0.274  1.0
  O  O16  1  0.187  0.164  0.557  1.0
  O  O17  1  0.836  0.813  0.943  1.0
  O  O18  1  0.813  0.836  0.443  1.0
  O  O19  1  0.164  0.187  0.057  1.0
  O  O20  1  0.065  0.935  0.750  1.0
  O  O21  1  0.935  0.065  0.250  1.0
[/CIF]
.