The compound described by K4U5Te2O21 crystallizes in the triclinic P-1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one O(10), one O(5), two equivalent O(2), and two equivalent O(6) atoms. In the second K site, K(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. There are three inequivalent U sites. In the first U site, U(1) is bonded to one O(1), one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form distorted UO7 pentagonal bipyramids that share  an edgeedge with one U(3)O6 octahedra and edges with two equivalent U(2)O7 pentagonal bipyramids. In the second U site, U(2) is bonded to one O(1), one O(11), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(3)O6 octahedra,  a cornercorner with one U(2)O7 pentagonal bipyramid, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. In the third U site, U(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing UO6 octahedra. Te(1) is bonded in a distorted T-shaped geometry to one O(3), one O(8), and one O(9) atom. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one K(2), one U(1), one U(2), and one U(3) atom to form distorted corner-sharing OKU3 trigonal pyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(2), two equivalent K(1), and one U(3) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one K(2), one U(1), and one Te(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one K(2) and one U(1) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one U(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one K(2), two equivalent K(1), and one U(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one U(1), one U(2), and one U(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Te(1) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one U(1), one U(2), and one Te(1) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one K(1), one K(2), and one U(1) atom. In the eleventh O site, O(11) is bonded in a linear geometry to two equivalent U(2) atoms. is represented by the CIF file [CIF]
data_K4U5Te2O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.969
_cell_length_b   7.118
_cell_length_c   11.382
_cell_angle_alpha   99.917
_cell_angle_beta   94.449
_cell_angle_gamma   100.038
_symmetry_Int_Tables_number   1
_cell_volume   544.306
_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
  K  K0  1  0.563  0.295  0.084  1.0
  K  K1  1  0.304  0.159  0.734  1.0
  K  K2  1  0.437  0.705  0.916  1.0
  K  K3  1  0.696  0.841  0.266  1.0
  U  U4  1  0.778  0.874  0.683  1.0
  U  U5  1  0.222  0.126  0.317  1.0
  U  U6  1  0.125  0.570  0.181  1.0
  U  U7  1  0.875  0.430  0.819  1.0
  U  U8  1  0.000  0.000  0.000  1.0
  Te  Te9  1  0.681  0.316  0.513  1.0
  Te  Te10  1  0.319  0.684  0.487  1.0
  O  O11  1  0.085  0.877  0.163  1.0
  O  O12  1  0.751  0.989  0.049  1.0
  O  O13  1  0.412  0.233  0.510  1.0
  O  O14  1  0.012  0.871  0.621  1.0
  O  O15  1  0.915  0.123  0.837  1.0
  O  O16  1  0.119  0.471  0.763  1.0
  O  O17  1  0.376  0.615  0.134  1.0
  O  O18  1  0.128  0.247  0.152  1.0
  O  O19  1  0.249  0.011  0.951  1.0
  O  O20  1  0.881  0.529  0.237  1.0
  O  O21  1  0.238  0.827  0.375  1.0
  O  O22  1  0.762  0.173  0.625  1.0
  O  O23  1  0.714  0.528  0.641  1.0
  O  O24  1  0.532  0.874  0.733  1.0
  O  O25  1  0.588  0.767  0.490  1.0
  O  O26  1  0.000  0.500  0.000  1.0
  O  O27  1  0.988  0.129  0.379  1.0
  O  O28  1  0.872  0.753  0.848  1.0
  O  O29  1  0.468  0.126  0.267  1.0
  O  O30  1  0.624  0.385  0.866  1.0
  O  O31  1  0.286  0.472  0.359  1.0
[/CIF]
.
The compound described by K4U5Te2O21 crystallizes in the triclinic P-1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one O(10), one O(5), two equivalent O(2), and two equivalent O(6) atoms. In the second K site, K(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. There are three inequivalent U sites. In the first U site, U(1) is bonded to one O(1), one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form distorted UO7 pentagonal bipyramids that share  an edgeedge with one U(3)O6 octahedra and edges with two equivalent U(2)O7 pentagonal bipyramids. In the second U site, U(2) is bonded to one O(1), one O(11), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted UO7 pentagonal bipyramids that share corners with two equivalent U(3)O6 octahedra,  a cornercorner with one U(2)O7 pentagonal bipyramid, and edges with two equivalent U(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. In the third U site, U(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing UO6 octahedra. Te(1) is bonded in a distorted T-shaped geometry to one O(3), one O(8), and one O(9) atom. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one K(2), one U(1), one U(2), and one U(3) atom to form distorted corner-sharing OKU3 trigonal pyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(2), two equivalent K(1), and one U(3) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one K(2), one U(1), and one Te(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one K(2) and one U(1) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one U(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one K(2), two equivalent K(1), and one U(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one U(1), one U(2), and one U(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one U(1), one U(2), and one Te(1) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one U(1), one U(2), and one Te(1) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one K(1), one K(2), and one U(1) atom. In the eleventh O site, O(11) is bonded in a linear geometry to two equivalent U(2) atoms. is represented by the CIF file [CIF]
data_K4U5Te2O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.969
_cell_length_b   7.118
_cell_length_c   11.382
_cell_angle_alpha   99.917
_cell_angle_beta   94.449
_cell_angle_gamma   100.038
_symmetry_Int_Tables_number   1
_cell_volume   544.306
_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
  K  K0  1  0.563  0.295  0.084  1.0
  K  K1  1  0.304  0.159  0.734  1.0
  K  K2  1  0.437  0.705  0.916  1.0
  K  K3  1  0.696  0.841  0.266  1.0
  U  U4  1  0.778  0.874  0.683  1.0
  U  U5  1  0.222  0.126  0.317  1.0
  U  U6  1  0.125  0.570  0.181  1.0
  U  U7  1  0.875  0.430  0.819  1.0
  U  U8  1  0.000  0.000  0.000  1.0
  Te  Te9  1  0.681  0.316  0.513  1.0
  Te  Te10  1  0.319  0.684  0.487  1.0
  O  O11  1  0.085  0.877  0.163  1.0
  O  O12  1  0.751  0.989  0.049  1.0
  O  O13  1  0.412  0.233  0.510  1.0
  O  O14  1  0.012  0.871  0.621  1.0
  O  O15  1  0.915  0.123  0.837  1.0
  O  O16  1  0.119  0.471  0.763  1.0
  O  O17  1  0.376  0.615  0.134  1.0
  O  O18  1  0.128  0.247  0.152  1.0
  O  O19  1  0.249  0.011  0.951  1.0
  O  O20  1  0.881  0.529  0.237  1.0
  O  O21  1  0.238  0.827  0.375  1.0
  O  O22  1  0.762  0.173  0.625  1.0
  O  O23  1  0.714  0.528  0.641  1.0
  O  O24  1  0.532  0.874  0.733  1.0
  O  O25  1  0.588  0.767  0.490  1.0
  O  O26  1  0.000  0.500  0.000  1.0
  O  O27  1  0.988  0.129  0.379  1.0
  O  O28  1  0.872  0.753  0.848  1.0
  O  O29  1  0.468  0.126  0.267  1.0
  O  O30  1  0.624  0.385  0.866  1.0
  O  O31  1  0.286  0.472  0.359  1.0
[/CIF]
.