The structure described by Ca2Se3O8 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(2), one O(4), one O(5), two equivalent O(7), and two equivalent O(8) atoms to form distorted edge-sharing CaO7 pentagonal bipyramids. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(2), one O(4), one O(7), one O(8), two equivalent O(1), and two equivalent O(6) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(3), one O(4), and one O(5) atom. In the third Se site, Se(3) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ca(2) and one Se(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one Se(3) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Se(2) and one Se(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(2), and one Se(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Ca(1) and one Se(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Ca(2) and one Se(1) atom. In the seventh O site, O(7) is bonded to one Ca(2), two equivalent Ca(1), and one Se(1) atom to form a mixture of distorted corner and edge-sharing OCa3Se tetrahedra. In the eighth O site, O(8) is bonded to one Ca(2), two equivalent Ca(1), and one Se(1) atom to form a mixture of distorted corner and edge-sharing OCa3Se tetrahedra. is represented by the CIF file [CIF]
data_Ca2Se3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.524
_cell_length_b   8.240
_cell_length_c   8.728
_cell_angle_alpha   92.606
_cell_angle_beta   95.999
_cell_angle_gamma   97.211
_symmetry_Int_Tables_number   1
_cell_volume   391.285
_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
  Ca  Ca0  1  0.292  0.161  0.961  1.0
  Ca  Ca1  1  0.708  0.839  0.039  1.0
  Ca  Ca2  1  0.242  0.956  0.347  1.0
  Ca  Ca3  1  0.758  0.044  0.653  1.0
  Se  Se4  1  0.823  0.192  0.239  1.0
  Se  Se5  1  0.177  0.808  0.761  1.0
  Se  Se6  1  0.226  0.556  0.183  1.0
  Se  Se7  1  0.774  0.444  0.817  1.0
  Se  Se8  1  0.274  0.324  0.578  1.0
  Se  Se9  1  0.726  0.676  0.422  1.0
  O  O10  1  0.548  0.814  0.479  1.0
  O  O11  1  0.452  0.186  0.521  1.0
  O  O12  1  0.868  0.766  0.281  1.0
  O  O13  1  0.132  0.234  0.719  1.0
  O  O14  1  0.495  0.478  0.688  1.0
  O  O15  1  0.505  0.522  0.312  1.0
  O  O16  1  0.683  0.254  0.869  1.0
  O  O17  1  0.317  0.746  0.131  1.0
  O  O18  1  0.748  0.573  0.963  1.0
  O  O19  1  0.252  0.427  0.037  1.0
  O  O20  1  0.087  0.871  0.584  1.0
  O  O21  1  0.913  0.129  0.416  1.0
  O  O22  1  0.452  0.926  0.821  1.0
  O  O23  1  0.548  0.074  0.179  1.0
  O  O24  1  0.991  0.917  0.860  1.0
  O  O25  1  0.009  0.083  0.140  1.0
[/CIF]
.
The structure described by Ca2Se3O8 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(2), one O(4), one O(5), two equivalent O(7), and two equivalent O(8) atoms to form distorted edge-sharing CaO7 pentagonal bipyramids. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(2), one O(4), one O(7), one O(8), two equivalent O(1), and two equivalent O(6) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(3), one O(4), and one O(5) atom. In the third Se site, Se(3) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ca(2) and one Se(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one Se(3) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Se(2) and one Se(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(2), and one Se(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Ca(1) and one Se(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Ca(2) and one Se(1) atom. In the seventh O site, O(7) is bonded to one Ca(2), two equivalent Ca(1), and one Se(1) atom to form a mixture of distorted corner and edge-sharing OCa3Se tetrahedra. In the eighth O site, O(8) is bonded to one Ca(2), two equivalent Ca(1), and one Se(1) atom to form a mixture of distorted corner and edge-sharing OCa3Se tetrahedra. is represented by the CIF file [CIF]
data_Ca2Se3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.524
_cell_length_b   8.240
_cell_length_c   8.728
_cell_angle_alpha   92.606
_cell_angle_beta   95.999
_cell_angle_gamma   97.211
_symmetry_Int_Tables_number   1
_cell_volume   391.285
_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
  Ca  Ca0  1  0.292  0.161  0.961  1.0
  Ca  Ca1  1  0.708  0.839  0.039  1.0
  Ca  Ca2  1  0.242  0.956  0.347  1.0
  Ca  Ca3  1  0.758  0.044  0.653  1.0
  Se  Se4  1  0.823  0.192  0.239  1.0
  Se  Se5  1  0.177  0.808  0.761  1.0
  Se  Se6  1  0.226  0.556  0.183  1.0
  Se  Se7  1  0.774  0.444  0.817  1.0
  Se  Se8  1  0.274  0.324  0.578  1.0
  Se  Se9  1  0.726  0.676  0.422  1.0
  O  O10  1  0.548  0.814  0.479  1.0
  O  O11  1  0.452  0.186  0.521  1.0
  O  O12  1  0.868  0.766  0.281  1.0
  O  O13  1  0.132  0.234  0.719  1.0
  O  O14  1  0.495  0.478  0.688  1.0
  O  O15  1  0.505  0.522  0.312  1.0
  O  O16  1  0.683  0.254  0.869  1.0
  O  O17  1  0.317  0.746  0.131  1.0
  O  O18  1  0.748  0.573  0.963  1.0
  O  O19  1  0.252  0.427  0.037  1.0
  O  O20  1  0.087  0.871  0.584  1.0
  O  O21  1  0.913  0.129  0.416  1.0
  O  O22  1  0.452  0.926  0.821  1.0
  O  O23  1  0.548  0.074  0.179  1.0
  O  O24  1  0.991  0.917  0.860  1.0
  O  O25  1  0.009  0.083  0.140  1.0
[/CIF]
.