The material described by CeSe2 crystallizes in the monoclinic P2/m space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(4), one Se(5), two equivalent Se(1), and two equivalent Se(3) atoms to form CeSe6 octahedra that share  a cornercorner with one Ce(1)Se6 octahedra, corners with two equivalent Ce(2)Se5 trigonal bipyramids, edges with two equivalent Ce(1)Se6 octahedra, and edges with two equivalent Ce(2)Se5 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the second Ce site, Ce(2) is bonded to one Se(1), one Se(2), one Se(3), and two equivalent Se(5) atoms to form distorted CeSe5 trigonal bipyramids that share corners with two equivalent Ce(1)Se6 octahedra, corners with three equivalent Ce(2)Se5 trigonal bipyramids, and edges with two equivalent Ce(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal planar geometry to one Ce(2) and two equivalent Ce(1) atoms. In the second Se site, Se(2) is bonded in a linear geometry to two equivalent Ce(2) atoms. In the third Se site, Se(3) is bonded in a distorted trigonal non-coplanar geometry to one Ce(2) and two equivalent Ce(1) atoms. In the fourth Se site, Se(4) is bonded in a linear geometry to two equivalent Ce(1) atoms. In the fifth Se site, Se(5) is bonded in a trigonal non-coplanar geometry to one Ce(1) and two equivalent Ce(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_CeSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.565
_cell_length_b   7.268
_cell_length_c   13.975
_cell_angle_alpha   79.448
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   455.894
_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  0.500  0.835  0.338  1.0
  Ce  Ce1  1  0.500  0.165  0.662  1.0
  Ce  Ce2  1  0.000  0.555  0.802  1.0
  Ce  Ce3  1  0.000  0.445  0.198  1.0
  Se  Se4  1  0.000  0.948  0.758  1.0
  Se  Se5  1  0.000  0.052  0.242  1.0
  Se  Se6  1  0.000  0.500  0.000  1.0
  Se  Se7  1  0.000  0.584  0.379  1.0
  Se  Se8  1  0.000  0.416  0.621  1.0
  Se  Se9  1  0.500  0.000  0.500  1.0
  Se  Se10  1  0.500  0.334  0.835  1.0
  Se  Se11  1  0.500  0.666  0.165  1.0
[/CIF]
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The material described by CeSe2 crystallizes in the monoclinic P2/m space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one Se(4), one Se(5), two equivalent Se(1), and two equivalent Se(3) atoms to form CeSe6 octahedra that share  a cornercorner with one Ce(1)Se6 octahedra, corners with two equivalent Ce(2)Se5 trigonal bipyramids, edges with two equivalent Ce(1)Se6 octahedra, and edges with two equivalent Ce(2)Se5 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the second Ce site, Ce(2) is bonded to one Se(1), one Se(2), one Se(3), and two equivalent Se(5) atoms to form distorted CeSe5 trigonal bipyramids that share corners with two equivalent Ce(1)Se6 octahedra, corners with three equivalent Ce(2)Se5 trigonal bipyramids, and edges with two equivalent Ce(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal planar geometry to one Ce(2) and two equivalent Ce(1) atoms. In the second Se site, Se(2) is bonded in a linear geometry to two equivalent Ce(2) atoms. In the third Se site, Se(3) is bonded in a distorted trigonal non-coplanar geometry to one Ce(2) and two equivalent Ce(1) atoms. In the fourth Se site, Se(4) is bonded in a linear geometry to two equivalent Ce(1) atoms. In the fifth Se site, Se(5) is bonded in a trigonal non-coplanar geometry to one Ce(1) and two equivalent Ce(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_CeSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.565
_cell_length_b   7.268
_cell_length_c   13.975
_cell_angle_alpha   79.448
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   455.894
_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  0.500  0.835  0.338  1.0
  Ce  Ce1  1  0.500  0.165  0.662  1.0
  Ce  Ce2  1  0.000  0.555  0.802  1.0
  Ce  Ce3  1  0.000  0.445  0.198  1.0
  Se  Se4  1  0.000  0.948  0.758  1.0
  Se  Se5  1  0.000  0.052  0.242  1.0
  Se  Se6  1  0.000  0.500  0.000  1.0
  Se  Se7  1  0.000  0.584  0.379  1.0
  Se  Se8  1  0.000  0.416  0.621  1.0
  Se  Se9  1  0.500  0.000  0.500  1.0
  Se  Se10  1  0.500  0.334  0.835  1.0
  Se  Se11  1  0.500  0.666  0.165  1.0
[/CIF]
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