The material described by U3O8 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(2), two equivalent O(4), and four equivalent O(1) atoms to form UO7 pentagonal bipyramids that share corners with two equivalent U(2)O6 octahedra, corners with three equivalent U(1)O7 pentagonal bipyramids,  an edgeedge with one U(2)O6 octahedra, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. In the second U site, U(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form UO6 octahedra that share corners with two equivalent U(2)O6 octahedra, corners with four equivalent U(1)O7 pentagonal bipyramids, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent U(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent U(2) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent U(1) atoms. is represented by the CIF card [CIF]
data_U3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.734
_cell_length_b   6.734
_cell_length_c   4.136
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   116.712
_symmetry_Int_Tables_number   1
_cell_volume   167.521
_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
  U  U0  1  0.319  0.681  0.000  1.0
  U  U1  1  0.681  0.319  0.000  1.0
  U  U2  1  0.000  0.000  0.000  1.0
  O  O3  1  0.038  0.325  0.000  1.0
  O  O4  1  0.962  0.675  0.000  1.0
  O  O5  1  0.325  0.038  0.000  1.0
  O  O6  1  0.500  0.500  0.000  1.0
  O  O7  1  0.000  0.000  0.500  1.0
  O  O8  1  0.685  0.315  0.500  1.0
  O  O9  1  0.315  0.685  0.500  1.0
  O  O10  1  0.675  0.962  0.000  1.0
[/CIF]
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The material described by U3O8 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to one O(2), two equivalent O(4), and four equivalent O(1) atoms to form UO7 pentagonal bipyramids that share corners with two equivalent U(2)O6 octahedra, corners with three equivalent U(1)O7 pentagonal bipyramids,  an edgeedge with one U(2)O6 octahedra, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. In the second U site, U(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form UO6 octahedra that share corners with two equivalent U(2)O6 octahedra, corners with four equivalent U(1)O7 pentagonal bipyramids, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one U(2) and two equivalent U(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent U(1) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent U(2) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent U(1) atoms. is represented by the CIF card [CIF]
data_U3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.734
_cell_length_b   6.734
_cell_length_c   4.136
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   116.712
_symmetry_Int_Tables_number   1
_cell_volume   167.521
_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
  U  U0  1  0.319  0.681  0.000  1.0
  U  U1  1  0.681  0.319  0.000  1.0
  U  U2  1  0.000  0.000  0.000  1.0
  O  O3  1  0.038  0.325  0.000  1.0
  O  O4  1  0.962  0.675  0.000  1.0
  O  O5  1  0.325  0.038  0.000  1.0
  O  O6  1  0.500  0.500  0.000  1.0
  O  O7  1  0.000  0.000  0.500  1.0
  O  O8  1  0.685  0.315  0.500  1.0
  O  O9  1  0.315  0.685  0.500  1.0
  O  O10  1  0.675  0.962  0.000  1.0
[/CIF]
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