The material described by U3O8 crystallizes in the orthorhombic Cmcm space group. There are three inequivalent U sites. In the first U site, U(1) is bonded to one O(4), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form UO7 pentagonal bipyramids that share corners with four equivalent U(3)O6 octahedra,  a cornercorner with one U(2)O7 pentagonal bipyramid,  an edgeedge with one U(3)O6 octahedra, and edges with two equivalent U(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 4-41°. In the second U site, U(2) is bonded to one O(4), two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form UO7 pentagonal bipyramids that share corners with two equivalent U(3)O6 octahedra,  a cornercorner with one U(1)O7 pentagonal bipyramid, corners with two equivalent U(2)O7 pentagonal bipyramids,  an edgeedge with one U(3)O6 octahedra, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 43°. In the third U site, U(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form a mixture of edge and corner-sharing UO6 octahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one U(1), one U(2), and one U(3) atom. In the second O site, O(2) is bonded in a linear geometry to one U(1) and one U(3) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one U(1), one U(2), and one U(3) atom. In the fourth O site, O(4) is bonded in a linear geometry to one U(1) and one U(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent U(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_U3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.745
_cell_length_b   6.745
_cell_length_c   8.308
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   117.170
_symmetry_Int_Tables_number   1
_cell_volume   336.248
_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
  U  U0  1  0.652  0.348  0.250  1.0
  U  U1  1  0.988  0.012  0.750  1.0
  U  U2  1  0.666  0.334  0.750  1.0
  U  U3  1  0.348  0.652  0.750  1.0
  U  U4  1  0.012  0.988  0.250  1.0
  U  U5  1  0.334  0.666  0.250  1.0
  O  O6  1  0.994  0.372  0.750  1.0
  O  O7  1  0.652  0.348  0.018  1.0
  O  O8  1  0.662  0.703  0.250  1.0
  O  O9  1  0.006  0.628  0.250  1.0
  O  O10  1  0.652  0.348  0.482  1.0
  O  O11  1  0.170  0.831  0.750  1.0
  O  O12  1  0.348  0.652  0.982  1.0
  O  O13  1  0.296  0.338  0.250  1.0
  O  O14  1  0.372  0.994  0.250  1.0
  O  O15  1  0.704  0.662  0.750  1.0
  O  O16  1  0.000  0.000  0.000  1.0
  O  O17  1  0.348  0.652  0.518  1.0
  O  O18  1  0.628  0.006  0.750  1.0
  O  O19  1  0.338  0.297  0.750  1.0
  O  O20  1  0.000  0.000  0.500  1.0
  O  O21  1  0.830  0.169  0.250  1.0
[/CIF]
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The material described by U3O8 crystallizes in the orthorhombic Cmcm space group. There are three inequivalent U sites. In the first U site, U(1) is bonded to one O(4), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form UO7 pentagonal bipyramids that share corners with four equivalent U(3)O6 octahedra,  a cornercorner with one U(2)O7 pentagonal bipyramid,  an edgeedge with one U(3)O6 octahedra, and edges with two equivalent U(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 4-41°. In the second U site, U(2) is bonded to one O(4), two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form UO7 pentagonal bipyramids that share corners with two equivalent U(3)O6 octahedra,  a cornercorner with one U(1)O7 pentagonal bipyramid, corners with two equivalent U(2)O7 pentagonal bipyramids,  an edgeedge with one U(3)O6 octahedra, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 43°. In the third U site, U(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form a mixture of edge and corner-sharing UO6 octahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one U(1), one U(2), and one U(3) atom. In the second O site, O(2) is bonded in a linear geometry to one U(1) and one U(3) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one U(1), one U(2), and one U(3) atom. In the fourth O site, O(4) is bonded in a linear geometry to one U(1) and one U(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent U(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_U3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.745
_cell_length_b   6.745
_cell_length_c   8.308
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   117.170
_symmetry_Int_Tables_number   1
_cell_volume   336.248
_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
  U  U0  1  0.652  0.348  0.250  1.0
  U  U1  1  0.988  0.012  0.750  1.0
  U  U2  1  0.666  0.334  0.750  1.0
  U  U3  1  0.348  0.652  0.750  1.0
  U  U4  1  0.012  0.988  0.250  1.0
  U  U5  1  0.334  0.666  0.250  1.0
  O  O6  1  0.994  0.372  0.750  1.0
  O  O7  1  0.652  0.348  0.018  1.0
  O  O8  1  0.662  0.703  0.250  1.0
  O  O9  1  0.006  0.628  0.250  1.0
  O  O10  1  0.652  0.348  0.482  1.0
  O  O11  1  0.170  0.831  0.750  1.0
  O  O12  1  0.348  0.652  0.982  1.0
  O  O13  1  0.296  0.338  0.250  1.0
  O  O14  1  0.372  0.994  0.250  1.0
  O  O15  1  0.704  0.662  0.750  1.0
  O  O16  1  0.000  0.000  0.000  1.0
  O  O17  1  0.348  0.652  0.518  1.0
  O  O18  1  0.628  0.006  0.750  1.0
  O  O19  1  0.338  0.297  0.750  1.0
  O  O20  1  0.000  0.000  0.500  1.0
  O  O21  1  0.830  0.169  0.250  1.0
[/CIF]
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