The compound described by Na2U2Si(O4F)2 crystallizes in the tetragonal I4_1/amd space group. Na(1) is bonded to four equivalent O(2) and two equivalent F(1) atoms to form distorted NaO4F2 octahedra that share corners with six equivalent U(1)O6F pentagonal bipyramids and faces with two equivalent Na(1)O4F2 octahedra. U(1) is bonded to two equivalent O(2), four equivalent O(1), and one F(1) atom to form distorted UO6F pentagonal bipyramids that share corners with six equivalent Na(1)O4F2 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent U(1)O6F pentagonal bipyramids, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. Si(1) is bonded to four equivalent O(1) atoms to form SiO4 tetrahedra that share corners with four equivalent U(1)O6F pentagonal bipyramids and edges with two equivalent U(1)O6F pentagonal bipyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent U(1) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one U(1) atom. F(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one U(1) atom. is represented by the CIF card [CIF]
data_Na2U2Si(O4F)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.535
_cell_length_b   10.535
_cell_length_c   10.535
_cell_angle_alpha   141.026
_cell_angle_beta   141.026
_cell_angle_gamma   56.299
_symmetry_Int_Tables_number   1
_cell_volume   458.849
_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
  Na  Na0  1  0.375  0.125  0.250  1.0
  Na  Na1  1  0.875  0.125  0.250  1.0
  Na  Na2  1  0.875  0.125  0.750  1.0
  Na  Na3  1  0.875  0.625  0.750  1.0
  U  U4  1  0.674  0.674  0.000  1.0
  U  U5  1  0.076  0.576  0.500  1.0
  U  U6  1  0.424  0.924  0.500  1.0
  U  U7  1  0.326  0.326  0.000  1.0
  Si  Si8  1  0.250  0.750  0.500  1.0
  Si  Si9  1  0.500  0.500  0.000  1.0
  O  O10  1  0.442  0.619  0.177  1.0
  O  O11  1  0.369  0.692  0.677  1.0
  O  O12  1  0.673  0.935  0.262  1.0
  O  O13  1  0.589  0.327  0.262  1.0
  O  O14  1  0.077  0.839  0.762  1.0
  O  O15  1  0.381  0.558  0.823  1.0
  O  O16  1  0.065  0.327  0.738  1.0
  O  O17  1  0.442  0.266  0.823  1.0
  O  O18  1  0.685  0.923  0.762  1.0
  O  O19  1  0.016  0.692  0.323  1.0
  O  O20  1  0.161  0.923  0.238  1.0
  O  O21  1  0.308  0.984  0.677  1.0
  O  O22  1  0.673  0.411  0.738  1.0
  O  O23  1  0.308  0.631  0.323  1.0
  O  O24  1  0.734  0.558  0.177  1.0
  O  O25  1  0.077  0.315  0.238  1.0
  F  F26  1  0.957  0.457  0.500  1.0
  F  F27  1  0.543  0.043  0.500  1.0
  F  F28  1  0.793  0.793  0.000  1.0
  F  F29  1  0.207  0.207  0.000  1.0
[/CIF]
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The compound described by Na2U2Si(O4F)2 crystallizes in the tetragonal I4_1/amd space group. Na(1) is bonded to four equivalent O(2) and two equivalent F(1) atoms to form distorted NaO4F2 octahedra that share corners with six equivalent U(1)O6F pentagonal bipyramids and faces with two equivalent Na(1)O4F2 octahedra. U(1) is bonded to two equivalent O(2), four equivalent O(1), and one F(1) atom to form distorted UO6F pentagonal bipyramids that share corners with six equivalent Na(1)O4F2 octahedra, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent U(1)O6F pentagonal bipyramids, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. Si(1) is bonded to four equivalent O(1) atoms to form SiO4 tetrahedra that share corners with four equivalent U(1)O6F pentagonal bipyramids and edges with two equivalent U(1)O6F pentagonal bipyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent U(1) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one U(1) atom. F(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one U(1) atom. is represented by the CIF card [CIF]
data_Na2U2Si(O4F)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.535
_cell_length_b   10.535
_cell_length_c   10.535
_cell_angle_alpha   141.026
_cell_angle_beta   141.026
_cell_angle_gamma   56.299
_symmetry_Int_Tables_number   1
_cell_volume   458.849
_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
  Na  Na0  1  0.375  0.125  0.250  1.0
  Na  Na1  1  0.875  0.125  0.250  1.0
  Na  Na2  1  0.875  0.125  0.750  1.0
  Na  Na3  1  0.875  0.625  0.750  1.0
  U  U4  1  0.674  0.674  0.000  1.0
  U  U5  1  0.076  0.576  0.500  1.0
  U  U6  1  0.424  0.924  0.500  1.0
  U  U7  1  0.326  0.326  0.000  1.0
  Si  Si8  1  0.250  0.750  0.500  1.0
  Si  Si9  1  0.500  0.500  0.000  1.0
  O  O10  1  0.442  0.619  0.177  1.0
  O  O11  1  0.369  0.692  0.677  1.0
  O  O12  1  0.673  0.935  0.262  1.0
  O  O13  1  0.589  0.327  0.262  1.0
  O  O14  1  0.077  0.839  0.762  1.0
  O  O15  1  0.381  0.558  0.823  1.0
  O  O16  1  0.065  0.327  0.738  1.0
  O  O17  1  0.442  0.266  0.823  1.0
  O  O18  1  0.685  0.923  0.762  1.0
  O  O19  1  0.016  0.692  0.323  1.0
  O  O20  1  0.161  0.923  0.238  1.0
  O  O21  1  0.308  0.984  0.677  1.0
  O  O22  1  0.673  0.411  0.738  1.0
  O  O23  1  0.308  0.631  0.323  1.0
  O  O24  1  0.734  0.558  0.177  1.0
  O  O25  1  0.077  0.315  0.238  1.0
  F  F26  1  0.957  0.457  0.500  1.0
  F  F27  1  0.543  0.043  0.500  1.0
  F  F28  1  0.793  0.793  0.000  1.0
  F  F29  1  0.207  0.207  0.000  1.0
[/CIF]
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