The material described by CeSe2 crystallizes in the triclinic P1 space group. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(1), one Se(3), one Se(5), one Se(6), and one Se(8) atom to form distorted corner-sharing CeSe5 trigonal bipyramids. In the second Ce site, Ce(2) is bonded to one Se(2), one Se(4), one Se(5), and one Se(6) atom to form CeSe4 tetrahedra that share  a cornercorner with one Ce(3)Se4 tetrahedra, corners with two equivalent Ce(4)Se4 tetrahedra, and corners with two equivalent Ce(1)Se5 trigonal bipyramids. In the third Ce site, Ce(3) is bonded to one Se(1), one Se(2), one Se(3), and one Se(7) atom to form CeSe4 tetrahedra that share  a cornercorner with one Ce(2)Se4 tetrahedra,  a cornercorner with one Ce(4)Se4 tetrahedra, and corners with two equivalent Ce(1)Se5 trigonal bipyramids. In the fourth Ce site, Ce(4) is bonded to one Se(4), one Se(6), one Se(7), and one Se(8) atom to form CeSe4 tetrahedra that share  a cornercorner with one Ce(3)Se4 tetrahedra, corners with two equivalent Ce(2)Se4 tetrahedra, and corners with two equivalent Ce(1)Se5 trigonal bipyramids. There are eight inequivalent Se sites. In the first Se site, Se(1) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(3) atom. In the second Se site, Se(2) is bonded in a bent 120 degrees geometry to one Ce(2) and one Ce(3) atom. In the third Se site, Se(3) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(3) atom. In the fourth Se site, Se(4) is bonded in a bent 120 degrees geometry to one Ce(2) and one Ce(4) atom. In the fifth Se site, Se(5) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom. In the sixth Se site, Se(6) is bonded in a trigonal planar geometry to one Ce(1), one Ce(2), and one Ce(4) atom. In the seventh Se site, Se(7) is bonded in a water-like geometry to one Ce(3) and one Ce(4) atom. In the eighth Se site, Se(8) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CeSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.837
_cell_length_b   9.169
_cell_length_c   9.392
_cell_angle_alpha   86.408
_cell_angle_beta   83.482
_cell_angle_gamma   64.668
_symmetry_Int_Tables_number   1
_cell_volume   683.334
_cell_formula_units_Z   4
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
  Ce  Ce0  1  0.834  0.719  0.184  1.0
  Ce  Ce1  1  0.316  0.199  0.071  1.0
  Ce  Ce2  1  0.703  0.980  0.678  1.0
  Ce  Ce3  1  0.812  0.213  0.276  1.0
  Se  Se4  1  0.865  0.839  0.910  1.0
  Se  Se5  1  0.375  0.149  0.784  1.0
  Se  Se6  1  0.813  0.747  0.478  1.0
  Se  Se7  1  0.134  0.033  0.173  1.0
  Se  Se8  1  0.166  0.504  0.163  1.0
  Se  Se9  1  0.603  0.068  0.223  1.0
  Se  Se10  1  0.808  0.206  0.565  1.0
  Se  Se11  1  0.700  0.506  0.148  1.0
[/CIF]
.
The material described by CeSe2 crystallizes in the triclinic P1 space group. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(1), one Se(3), one Se(5), one Se(6), and one Se(8) atom to form distorted corner-sharing CeSe5 trigonal bipyramids. In the second Ce site, Ce(2) is bonded to one Se(2), one Se(4), one Se(5), and one Se(6) atom to form CeSe4 tetrahedra that share  a cornercorner with one Ce(3)Se4 tetrahedra, corners with two equivalent Ce(4)Se4 tetrahedra, and corners with two equivalent Ce(1)Se5 trigonal bipyramids. In the third Ce site, Ce(3) is bonded to one Se(1), one Se(2), one Se(3), and one Se(7) atom to form CeSe4 tetrahedra that share  a cornercorner with one Ce(2)Se4 tetrahedra,  a cornercorner with one Ce(4)Se4 tetrahedra, and corners with two equivalent Ce(1)Se5 trigonal bipyramids. In the fourth Ce site, Ce(4) is bonded to one Se(4), one Se(6), one Se(7), and one Se(8) atom to form CeSe4 tetrahedra that share  a cornercorner with one Ce(3)Se4 tetrahedra, corners with two equivalent Ce(2)Se4 tetrahedra, and corners with two equivalent Ce(1)Se5 trigonal bipyramids. There are eight inequivalent Se sites. In the first Se site, Se(1) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(3) atom. In the second Se site, Se(2) is bonded in a bent 120 degrees geometry to one Ce(2) and one Ce(3) atom. In the third Se site, Se(3) is bonded in a bent 150 degrees geometry to one Ce(1) and one Ce(3) atom. In the fourth Se site, Se(4) is bonded in a bent 120 degrees geometry to one Ce(2) and one Ce(4) atom. In the fifth Se site, Se(5) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(2) atom. In the sixth Se site, Se(6) is bonded in a trigonal planar geometry to one Ce(1), one Ce(2), and one Ce(4) atom. In the seventh Se site, Se(7) is bonded in a water-like geometry to one Ce(3) and one Ce(4) atom. In the eighth Se site, Se(8) is bonded in a bent 120 degrees geometry to one Ce(1) and one Ce(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CeSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.837
_cell_length_b   9.169
_cell_length_c   9.392
_cell_angle_alpha   86.408
_cell_angle_beta   83.482
_cell_angle_gamma   64.668
_symmetry_Int_Tables_number   1
_cell_volume   683.334
_cell_formula_units_Z   4
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
  Ce  Ce0  1  0.834  0.719  0.184  1.0
  Ce  Ce1  1  0.316  0.199  0.071  1.0
  Ce  Ce2  1  0.703  0.980  0.678  1.0
  Ce  Ce3  1  0.812  0.213  0.276  1.0
  Se  Se4  1  0.865  0.839  0.910  1.0
  Se  Se5  1  0.375  0.149  0.784  1.0
  Se  Se6  1  0.813  0.747  0.478  1.0
  Se  Se7  1  0.134  0.033  0.173  1.0
  Se  Se8  1  0.166  0.504  0.163  1.0
  Se  Se9  1  0.603  0.068  0.223  1.0
  Se  Se10  1  0.808  0.206  0.565  1.0
  Se  Se11  1  0.700  0.506  0.148  1.0
[/CIF]
.