The material described by U2Ce2O9 crystallizes in the tetragonal I4/mmm space group. U(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(2) and eight equivalent O(1) atoms. Ce(1) is bonded in a distorted q6 geometry to one O(2) and eight equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent U(1) and two equivalent Ce(1) atoms to form OCe2U2 tetrahedra that share corners with three equivalent O(2)Ce2U4 octahedra, corners with sixteen equivalent O(1)Ce2U2 tetrahedra, edges with six equivalent O(1)Ce2U2 tetrahedra, and  a faceface with one O(2)Ce2U4 octahedra. The corner-sharing octahedral tilt angles range from 49-57°. In the second O site, O(2) is bonded to four equivalent U(1) and two equivalent Ce(1) atoms to form OCe2U4 octahedra that share corners with four equivalent O(2)Ce2U4 octahedra, corners with twenty-four equivalent O(1)Ce2U2 tetrahedra, and faces with eight equivalent O(1)Ce2U2 tetrahedra. The corner-sharing octahedra are not tilted. is represented by the CIF file [CIF]
data_Ce2U2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.627
_cell_length_b   6.627
_cell_length_c   6.627
_cell_angle_alpha   131.625
_cell_angle_beta   131.625
_cell_angle_gamma   70.822
_symmetry_Int_Tables_number   1
_cell_volume   159.267
_cell_formula_units_Z   1
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  0.732  0.732  0.000  1.0
  Ce  Ce1  1  0.268  0.268  0.000  1.0
  U  U2  1  0.000  0.500  0.500  1.0
  U  U3  1  0.500  0.000  0.500  1.0
  O  O4  1  0.358  0.358  0.469  1.0
  O  O5  1  0.642  0.111  0.000  1.0
  O  O6  1  0.889  0.889  0.531  1.0
  O  O7  1  0.111  0.642  0.000  1.0
  O  O8  1  0.111  0.111  0.469  1.0
  O  O9  1  0.358  0.889  0.000  1.0
  O  O10  1  0.642  0.642  0.531  1.0
  O  O11  1  0.889  0.358  0.000  1.0
  O  O12  1  0.500  0.500  0.000  1.0
[/CIF]
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The material described by U2Ce2O9 crystallizes in the tetragonal I4/mmm space group. U(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(2) and eight equivalent O(1) atoms. Ce(1) is bonded in a distorted q6 geometry to one O(2) and eight equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent U(1) and two equivalent Ce(1) atoms to form OCe2U2 tetrahedra that share corners with three equivalent O(2)Ce2U4 octahedra, corners with sixteen equivalent O(1)Ce2U2 tetrahedra, edges with six equivalent O(1)Ce2U2 tetrahedra, and  a faceface with one O(2)Ce2U4 octahedra. The corner-sharing octahedral tilt angles range from 49-57°. In the second O site, O(2) is bonded to four equivalent U(1) and two equivalent Ce(1) atoms to form OCe2U4 octahedra that share corners with four equivalent O(2)Ce2U4 octahedra, corners with twenty-four equivalent O(1)Ce2U2 tetrahedra, and faces with eight equivalent O(1)Ce2U2 tetrahedra. The corner-sharing octahedra are not tilted. is represented by the CIF file [CIF]
data_Ce2U2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.627
_cell_length_b   6.627
_cell_length_c   6.627
_cell_angle_alpha   131.625
_cell_angle_beta   131.625
_cell_angle_gamma   70.822
_symmetry_Int_Tables_number   1
_cell_volume   159.267
_cell_formula_units_Z   1
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  0.732  0.732  0.000  1.0
  Ce  Ce1  1  0.268  0.268  0.000  1.0
  U  U2  1  0.000  0.500  0.500  1.0
  U  U3  1  0.500  0.000  0.500  1.0
  O  O4  1  0.358  0.358  0.469  1.0
  O  O5  1  0.642  0.111  0.000  1.0
  O  O6  1  0.889  0.889  0.531  1.0
  O  O7  1  0.111  0.642  0.000  1.0
  O  O8  1  0.111  0.111  0.469  1.0
  O  O9  1  0.358  0.889  0.000  1.0
  O  O10  1  0.642  0.642  0.531  1.0
  O  O11  1  0.889  0.358  0.000  1.0
  O  O12  1  0.500  0.500  0.000  1.0
[/CIF]
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