The structure described by U8FeSe17 crystallizes in the monoclinic C2/m space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one Se(2), one Se(3), one Se(4), one Se(5), one Se(6), one Se(7), and two equivalent Se(1) atoms. In the second U site, U(2) is bonded in a 8-coordinate geometry to one Se(3), one Se(4), one Se(5), one Se(7), and four equivalent Se(1) atoms. In the third U site, U(3) is bonded in a 8-coordinate geometry to one Se(3), one Se(5), two equivalent Se(6), and four equivalent Se(2) atoms. Fe(1) is bonded in an octahedral geometry to two equivalent Se(4) and four equivalent Se(2) atoms. There are seven inequivalent Se sites. In the first Se site, Se(6) is bonded to two equivalent U(1) and two equivalent U(3) atoms to form SeU4 trigonal pyramids that share corners with two equivalent Se(7)U6 octahedra, corners with six equivalent Se(2)U3Fe tetrahedra, edges with two equivalent Se(2)U3Fe tetrahedra, and  an edgeedge with one Se(6)U4 trigonal pyramid. The corner-sharing octahedral tilt angles are 38°. In the second Se site, Se(7) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form SeU6 octahedra that share corners with four equivalent Se(2)U3Fe tetrahedra and corners with four equivalent Se(6)U4 trigonal pyramids. In the third Se site, Se(1) is bonded in a rectangular see-saw-like geometry to two equivalent U(1) and two equivalent U(2) atoms. In the fourth Se site, Se(2) is bonded to one U(1), two equivalent U(3), and one Fe(1) atom to form distorted SeU3Fe tetrahedra that share  a cornercorner with one Se(7)U6 octahedra, corners with five equivalent Se(2)U3Fe tetrahedra, corners with three equivalent Se(6)U4 trigonal pyramids, edges with two equivalent Se(2)U3Fe tetrahedra, and  an edgeedge with one Se(6)U4 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. In the fifth Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one U(2), one U(3), and two equivalent U(1) atoms. In the sixth Se site, Se(4) is bonded in a distorted rectangular see-saw-like geometry to one U(2), two equivalent U(1), and one Fe(1) atom. In the seventh Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one U(2), one U(3), and two equivalent U(1) atoms. is represented by the CIF file [CIF]
data_U8FeSe17
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.213
_cell_length_b   8.213
_cell_length_c   10.828
_cell_angle_alpha   80.491
_cell_angle_beta   80.491
_cell_angle_gamma   64.285
_symmetry_Int_Tables_number   1
_cell_volume   645.404
_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  0.819  0.300  0.299  1.0
  U  U1  1  0.300  0.819  0.299  1.0
  U  U2  1  0.181  0.700  0.701  1.0
  U  U3  1  0.700  0.181  0.701  1.0
  U  U4  1  0.202  0.202  0.543  1.0
  U  U5  1  0.798  0.798  0.457  1.0
  U  U6  1  0.681  0.681  0.985  1.0
  U  U7  1  0.319  0.319  0.015  1.0
  Fe  Fe8  1  0.000  0.000  0.000  1.0
  Se  Se9  1  0.819  0.434  0.536  1.0
  Se  Se10  1  0.434  0.819  0.536  1.0
  Se  Se11  1  0.181  0.566  0.464  1.0
  Se  Se12  1  0.566  0.181  0.464  1.0
  Se  Se13  1  0.944  0.325  0.027  1.0
  Se  Se14  1  0.325  0.944  0.027  1.0
  Se  Se15  1  0.056  0.675  0.973  1.0
  Se  Se16  1  0.675  0.056  0.973  1.0
  Se  Se17  1  0.214  0.214  0.277  1.0
  Se  Se18  1  0.786  0.786  0.723  1.0
  Se  Se19  1  0.057  0.057  0.775  1.0
  Se  Se20  1  0.943  0.943  0.225  1.0
  Se  Se21  1  0.301  0.301  0.755  1.0
  Se  Se22  1  0.699  0.699  0.245  1.0
  Se  Se23  1  0.521  0.521  0.830  1.0
  Se  Se24  1  0.479  0.479  0.170  1.0
  Se  Se25  1  0.000  0.000  0.500  1.0
[/CIF]
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The structure described by U8FeSe17 crystallizes in the monoclinic C2/m space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one Se(2), one Se(3), one Se(4), one Se(5), one Se(6), one Se(7), and two equivalent Se(1) atoms. In the second U site, U(2) is bonded in a 8-coordinate geometry to one Se(3), one Se(4), one Se(5), one Se(7), and four equivalent Se(1) atoms. In the third U site, U(3) is bonded in a 8-coordinate geometry to one Se(3), one Se(5), two equivalent Se(6), and four equivalent Se(2) atoms. Fe(1) is bonded in an octahedral geometry to two equivalent Se(4) and four equivalent Se(2) atoms. There are seven inequivalent Se sites. In the first Se site, Se(6) is bonded to two equivalent U(1) and two equivalent U(3) atoms to form SeU4 trigonal pyramids that share corners with two equivalent Se(7)U6 octahedra, corners with six equivalent Se(2)U3Fe tetrahedra, edges with two equivalent Se(2)U3Fe tetrahedra, and  an edgeedge with one Se(6)U4 trigonal pyramid. The corner-sharing octahedral tilt angles are 38°. In the second Se site, Se(7) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form SeU6 octahedra that share corners with four equivalent Se(2)U3Fe tetrahedra and corners with four equivalent Se(6)U4 trigonal pyramids. In the third Se site, Se(1) is bonded in a rectangular see-saw-like geometry to two equivalent U(1) and two equivalent U(2) atoms. In the fourth Se site, Se(2) is bonded to one U(1), two equivalent U(3), and one Fe(1) atom to form distorted SeU3Fe tetrahedra that share  a cornercorner with one Se(7)U6 octahedra, corners with five equivalent Se(2)U3Fe tetrahedra, corners with three equivalent Se(6)U4 trigonal pyramids, edges with two equivalent Se(2)U3Fe tetrahedra, and  an edgeedge with one Se(6)U4 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. In the fifth Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one U(2), one U(3), and two equivalent U(1) atoms. In the sixth Se site, Se(4) is bonded in a distorted rectangular see-saw-like geometry to one U(2), two equivalent U(1), and one Fe(1) atom. In the seventh Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one U(2), one U(3), and two equivalent U(1) atoms. is represented by the CIF file [CIF]
data_U8FeSe17
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.213
_cell_length_b   8.213
_cell_length_c   10.828
_cell_angle_alpha   80.491
_cell_angle_beta   80.491
_cell_angle_gamma   64.285
_symmetry_Int_Tables_number   1
_cell_volume   645.404
_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  0.819  0.300  0.299  1.0
  U  U1  1  0.300  0.819  0.299  1.0
  U  U2  1  0.181  0.700  0.701  1.0
  U  U3  1  0.700  0.181  0.701  1.0
  U  U4  1  0.202  0.202  0.543  1.0
  U  U5  1  0.798  0.798  0.457  1.0
  U  U6  1  0.681  0.681  0.985  1.0
  U  U7  1  0.319  0.319  0.015  1.0
  Fe  Fe8  1  0.000  0.000  0.000  1.0
  Se  Se9  1  0.819  0.434  0.536  1.0
  Se  Se10  1  0.434  0.819  0.536  1.0
  Se  Se11  1  0.181  0.566  0.464  1.0
  Se  Se12  1  0.566  0.181  0.464  1.0
  Se  Se13  1  0.944  0.325  0.027  1.0
  Se  Se14  1  0.325  0.944  0.027  1.0
  Se  Se15  1  0.056  0.675  0.973  1.0
  Se  Se16  1  0.675  0.056  0.973  1.0
  Se  Se17  1  0.214  0.214  0.277  1.0
  Se  Se18  1  0.786  0.786  0.723  1.0
  Se  Se19  1  0.057  0.057  0.775  1.0
  Se  Se20  1  0.943  0.943  0.225  1.0
  Se  Se21  1  0.301  0.301  0.755  1.0
  Se  Se22  1  0.699  0.699  0.245  1.0
  Se  Se23  1  0.521  0.521  0.830  1.0
  Se  Se24  1  0.479  0.479  0.170  1.0
  Se  Se25  1  0.000  0.000  0.500  1.0
[/CIF]
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