The material described by K4Nb11Al2O20F crystallizes in the tetragonal I4/mmm space group. K(1) is bonded in a 11-coordinate geometry to two equivalent O(3), four equivalent O(1), four equivalent O(2), and one F(1) atom. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form NbO5 square pyramids that share corners with two equivalent Nb(3)O4F square pyramids, corners with three equivalent Nb(1)O5 square pyramids, corners with two equivalent Al(1)O4 tetrahedra, and  an edgeedge with one Nb(1)O5 square pyramid. In the second Nb site, Nb(2) is bonded in a square co-planar geometry to four equivalent O(3) atoms. In the third Nb site, Nb(3) is bonded to four equivalent O(1) and one F(1) atom to form NbO4F square pyramids that share  a cornercorner with one Nb(3)O4F square pyramid and corners with eight equivalent Nb(1)O5 square pyramids. Al(1) is bonded to four equivalent O(2) atoms to form AlO4 tetrahedra that share corners with eight equivalent Nb(1)O5 square pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent K(1), one Nb(3), and two equivalent Nb(1) atoms to form distorted OK2Nb3 trigonal bipyramids that share corners with three equivalent O(1)K2Nb3 trigonal bipyramids, corners with three equivalent O(3)K2Nb3 trigonal bipyramids, edges with four equivalent O(1)K2Nb3 trigonal bipyramids,  a faceface with one F(1)K4Nb2 octahedra, and  a faceface with one O(3)K2Nb3 trigonal bipyramid. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent K(1), two equivalent Nb(1), and one Al(1) atom. In the third O site, O(3) is bonded to two equivalent K(1), one Nb(2), and two equivalent Nb(1) atoms to form distorted OK2Nb3 trigonal bipyramids that share corners with five equivalent O(3)K2Nb3 trigonal bipyramids, corners with six equivalent O(1)K2Nb3 trigonal bipyramids,  an edgeedge with one F(1)K4Nb2 octahedra, and faces with two equivalent O(1)K2Nb3 trigonal bipyramids. F(1) is bonded to four equivalent K(1) and two equivalent Nb(3) atoms to form FK4Nb2 octahedra that share edges with four equivalent O(3)K2Nb3 trigonal bipyramids and faces with eight equivalent O(1)K2Nb3 trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_K4Nb11Al2O20F
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.993
_cell_length_b   8.993
_cell_length_c   8.993
_cell_angle_alpha   120.624
_cell_angle_beta   120.624
_cell_angle_gamma   88.922
_symmetry_Int_Tables_number   1
_cell_volume   509.280
_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  0.808  0.500  0.308  1.0
  K  K1  1  0.500  0.192  0.692  1.0
  K  K2  1  0.500  0.808  0.308  1.0
  K  K3  1  0.192  0.500  0.692  1.0
  Nb  Nb4  1  0.999  0.676  0.000  1.0
  Nb  Nb5  1  0.676  0.999  0.000  1.0
  Nb  Nb6  1  0.676  0.676  0.677  1.0
  Nb  Nb7  1  0.001  0.001  0.677  1.0
  Nb  Nb8  1  0.999  0.999  0.323  1.0
  Nb  Nb9  1  0.324  0.324  0.323  1.0
  Nb  Nb10  1  0.324  0.001  0.000  1.0
  Nb  Nb11  1  0.000  0.000  0.000  1.0
  Nb  Nb12  1  0.685  0.685  0.000  1.0
  Nb  Nb13  1  0.315  0.315  0.000  1.0
  Nb  Nb14  1  0.001  0.324  0.000  1.0
  Al  Al15  1  0.750  0.250  0.500  1.0
  Al  Al16  1  0.250  0.750  0.500  1.0
  O  O17  1  0.160  0.491  0.000  1.0
  O  O18  1  0.840  0.509  0.000  1.0
  O  O19  1  0.166  0.827  0.661  1.0
  O  O20  1  0.166  0.505  0.339  1.0
  O  O21  1  0.160  0.160  0.669  1.0
  O  O22  1  0.509  0.509  0.669  1.0
  O  O23  1  0.830  0.830  0.661  1.0
  O  O24  1  0.170  0.830  0.000  1.0
  O  O25  1  0.509  0.840  0.000  1.0
  O  O26  1  0.830  0.170  0.000  1.0
  O  O27  1  0.491  0.160  0.000  1.0
  O  O28  1  0.170  0.170  0.339  1.0
  O  O29  1  0.834  0.495  0.661  1.0
  O  O30  1  0.491  0.491  0.331  1.0
  O  O31  1  0.840  0.840  0.331  1.0
  O  O32  1  0.505  0.166  0.339  1.0
  O  O33  1  0.834  0.173  0.339  1.0
  O  O34  1  0.827  0.166  0.661  1.0
  O  O35  1  0.495  0.834  0.661  1.0
  O  O36  1  0.173  0.834  0.339  1.0
  F  F37  1  0.500  0.500  0.000  1.0
[/CIF]
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The material described by K4Nb11Al2O20F crystallizes in the tetragonal I4/mmm space group. K(1) is bonded in a 11-coordinate geometry to two equivalent O(3), four equivalent O(1), four equivalent O(2), and one F(1) atom. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form NbO5 square pyramids that share corners with two equivalent Nb(3)O4F square pyramids, corners with three equivalent Nb(1)O5 square pyramids, corners with two equivalent Al(1)O4 tetrahedra, and  an edgeedge with one Nb(1)O5 square pyramid. In the second Nb site, Nb(2) is bonded in a square co-planar geometry to four equivalent O(3) atoms. In the third Nb site, Nb(3) is bonded to four equivalent O(1) and one F(1) atom to form NbO4F square pyramids that share  a cornercorner with one Nb(3)O4F square pyramid and corners with eight equivalent Nb(1)O5 square pyramids. Al(1) is bonded to four equivalent O(2) atoms to form AlO4 tetrahedra that share corners with eight equivalent Nb(1)O5 square pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent K(1), one Nb(3), and two equivalent Nb(1) atoms to form distorted OK2Nb3 trigonal bipyramids that share corners with three equivalent O(1)K2Nb3 trigonal bipyramids, corners with three equivalent O(3)K2Nb3 trigonal bipyramids, edges with four equivalent O(1)K2Nb3 trigonal bipyramids,  a faceface with one F(1)K4Nb2 octahedra, and  a faceface with one O(3)K2Nb3 trigonal bipyramid. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent K(1), two equivalent Nb(1), and one Al(1) atom. In the third O site, O(3) is bonded to two equivalent K(1), one Nb(2), and two equivalent Nb(1) atoms to form distorted OK2Nb3 trigonal bipyramids that share corners with five equivalent O(3)K2Nb3 trigonal bipyramids, corners with six equivalent O(1)K2Nb3 trigonal bipyramids,  an edgeedge with one F(1)K4Nb2 octahedra, and faces with two equivalent O(1)K2Nb3 trigonal bipyramids. F(1) is bonded to four equivalent K(1) and two equivalent Nb(3) atoms to form FK4Nb2 octahedra that share edges with four equivalent O(3)K2Nb3 trigonal bipyramids and faces with eight equivalent O(1)K2Nb3 trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_K4Nb11Al2O20F
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.993
_cell_length_b   8.993
_cell_length_c   8.993
_cell_angle_alpha   120.624
_cell_angle_beta   120.624
_cell_angle_gamma   88.922
_symmetry_Int_Tables_number   1
_cell_volume   509.280
_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  0.808  0.500  0.308  1.0
  K  K1  1  0.500  0.192  0.692  1.0
  K  K2  1  0.500  0.808  0.308  1.0
  K  K3  1  0.192  0.500  0.692  1.0
  Nb  Nb4  1  0.999  0.676  0.000  1.0
  Nb  Nb5  1  0.676  0.999  0.000  1.0
  Nb  Nb6  1  0.676  0.676  0.677  1.0
  Nb  Nb7  1  0.001  0.001  0.677  1.0
  Nb  Nb8  1  0.999  0.999  0.323  1.0
  Nb  Nb9  1  0.324  0.324  0.323  1.0
  Nb  Nb10  1  0.324  0.001  0.000  1.0
  Nb  Nb11  1  0.000  0.000  0.000  1.0
  Nb  Nb12  1  0.685  0.685  0.000  1.0
  Nb  Nb13  1  0.315  0.315  0.000  1.0
  Nb  Nb14  1  0.001  0.324  0.000  1.0
  Al  Al15  1  0.750  0.250  0.500  1.0
  Al  Al16  1  0.250  0.750  0.500  1.0
  O  O17  1  0.160  0.491  0.000  1.0
  O  O18  1  0.840  0.509  0.000  1.0
  O  O19  1  0.166  0.827  0.661  1.0
  O  O20  1  0.166  0.505  0.339  1.0
  O  O21  1  0.160  0.160  0.669  1.0
  O  O22  1  0.509  0.509  0.669  1.0
  O  O23  1  0.830  0.830  0.661  1.0
  O  O24  1  0.170  0.830  0.000  1.0
  O  O25  1  0.509  0.840  0.000  1.0
  O  O26  1  0.830  0.170  0.000  1.0
  O  O27  1  0.491  0.160  0.000  1.0
  O  O28  1  0.170  0.170  0.339  1.0
  O  O29  1  0.834  0.495  0.661  1.0
  O  O30  1  0.491  0.491  0.331  1.0
  O  O31  1  0.840  0.840  0.331  1.0
  O  O32  1  0.505  0.166  0.339  1.0
  O  O33  1  0.834  0.173  0.339  1.0
  O  O34  1  0.827  0.166  0.661  1.0
  O  O35  1  0.495  0.834  0.661  1.0
  O  O36  1  0.173  0.834  0.339  1.0
  F  F37  1  0.500  0.500  0.000  1.0
[/CIF]
.