The material described by EuK2Nb5O15 crystallizes in the tetragonal P4/mbm space group. K(1) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(2), and four equivalent O(3) atoms. Eu(1) is bonded to four equivalent O(4) and eight equivalent O(5) atoms to form EuO12 cuboctahedra that share faces with two equivalent Eu(1)O12 cuboctahedra and faces with eight equivalent Nb(2)O6 octahedra. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-33°. In the second Nb site, Nb(2) is bonded to one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with five equivalent Nb(2)O6 octahedra, and faces with two equivalent Eu(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 10-35°. There are five inequivalent O sites. In the first O site, O(5) is bonded in a distorted linear geometry to two equivalent Eu(1) and two equivalent Nb(2) atoms. In the second O site, O(1) is bonded in a linear geometry to two equivalent K(1) and two equivalent Nb(1) atoms. In the third O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Nb(2) atoms. In the fourth O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), one Nb(1), and one Nb(2) atom. In the fifth O site, O(4) is bonded in a 2-coordinate geometry to one Eu(1) and two equivalent Nb(2) atoms. is represented by the CIF file [CIF]
data_K2EuNb5O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.746
_cell_length_b   12.746
_cell_length_c   3.971
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   645.099
_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
  K  K0  1  0.331  0.169  0.500  1.0
  K  K1  1  0.669  0.831  0.500  1.0
  K  K2  1  0.169  0.669  0.500  1.0
  K  K3  1  0.831  0.331  0.500  1.0
  Eu  Eu4  1  0.500  0.500  0.500  1.0
  Eu  Eu5  1  0.000  0.000  0.500  1.0
  Nb  Nb6  1  0.500  0.000  0.000  1.0
  Nb  Nb7  1  0.000  0.500  0.000  1.0
  Nb  Nb8  1  0.214  0.926  0.000  1.0
  Nb  Nb9  1  0.786  0.074  0.000  1.0
  Nb  Nb10  1  0.286  0.426  0.000  1.0
  Nb  Nb11  1  0.714  0.574  0.000  1.0
  Nb  Nb12  1  0.926  0.786  0.000  1.0
  Nb  Nb13  1  0.074  0.214  0.000  1.0
  Nb  Nb14  1  0.426  0.714  0.000  1.0
  Nb  Nb15  1  0.574  0.286  0.000  1.0
  O  O16  1  0.500  0.000  0.500  1.0
  O  O17  1  0.000  0.500  0.500  1.0
  O  O18  1  0.286  0.786  0.000  1.0
  O  O19  1  0.714  0.214  0.000  1.0
  O  O20  1  0.214  0.286  0.000  1.0
  O  O21  1  0.786  0.714  0.000  1.0
  O  O22  1  0.157  0.504  0.000  1.0
  O  O23  1  0.843  0.496  0.000  1.0
  O  O24  1  0.343  0.004  0.000  1.0
  O  O25  1  0.657  0.996  0.000  1.0
  O  O26  1  0.504  0.843  0.000  1.0
  O  O27  1  0.496  0.157  0.000  1.0
  O  O28  1  0.004  0.657  0.000  1.0
  O  O29  1  0.996  0.343  0.000  1.0
  O  O30  1  0.432  0.698  0.500  1.0
  O  O31  1  0.568  0.302  0.500  1.0
  O  O32  1  0.068  0.198  0.500  1.0
  O  O33  1  0.932  0.802  0.500  1.0
  O  O34  1  0.698  0.568  0.500  1.0
  O  O35  1  0.302  0.432  0.500  1.0
  O  O36  1  0.198  0.932  0.500  1.0
  O  O37  1  0.802  0.068  0.500  1.0
  O  O38  1  0.565  0.632  0.000  1.0
  O  O39  1  0.435  0.368  0.000  1.0
  O  O40  1  0.935  0.132  0.000  1.0
  O  O41  1  0.065  0.868  0.000  1.0
  O  O42  1  0.632  0.435  0.000  1.0
  O  O43  1  0.368  0.565  0.000  1.0
  O  O44  1  0.132  0.065  0.000  1.0
  O  O45  1  0.868  0.935  0.000  1.0
[/CIF]
.
The material described by EuK2Nb5O15 crystallizes in the tetragonal P4/mbm space group. K(1) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(2), and four equivalent O(3) atoms. Eu(1) is bonded to four equivalent O(4) and eight equivalent O(5) atoms to form EuO12 cuboctahedra that share faces with two equivalent Eu(1)O12 cuboctahedra and faces with eight equivalent Nb(2)O6 octahedra. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-33°. In the second Nb site, Nb(2) is bonded to one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with five equivalent Nb(2)O6 octahedra, and faces with two equivalent Eu(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 10-35°. There are five inequivalent O sites. In the first O site, O(5) is bonded in a distorted linear geometry to two equivalent Eu(1) and two equivalent Nb(2) atoms. In the second O site, O(1) is bonded in a linear geometry to two equivalent K(1) and two equivalent Nb(1) atoms. In the third O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Nb(2) atoms. In the fourth O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), one Nb(1), and one Nb(2) atom. In the fifth O site, O(4) is bonded in a 2-coordinate geometry to one Eu(1) and two equivalent Nb(2) atoms. is represented by the CIF file [CIF]
data_K2EuNb5O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.746
_cell_length_b   12.746
_cell_length_c   3.971
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   645.099
_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
  K  K0  1  0.331  0.169  0.500  1.0
  K  K1  1  0.669  0.831  0.500  1.0
  K  K2  1  0.169  0.669  0.500  1.0
  K  K3  1  0.831  0.331  0.500  1.0
  Eu  Eu4  1  0.500  0.500  0.500  1.0
  Eu  Eu5  1  0.000  0.000  0.500  1.0
  Nb  Nb6  1  0.500  0.000  0.000  1.0
  Nb  Nb7  1  0.000  0.500  0.000  1.0
  Nb  Nb8  1  0.214  0.926  0.000  1.0
  Nb  Nb9  1  0.786  0.074  0.000  1.0
  Nb  Nb10  1  0.286  0.426  0.000  1.0
  Nb  Nb11  1  0.714  0.574  0.000  1.0
  Nb  Nb12  1  0.926  0.786  0.000  1.0
  Nb  Nb13  1  0.074  0.214  0.000  1.0
  Nb  Nb14  1  0.426  0.714  0.000  1.0
  Nb  Nb15  1  0.574  0.286  0.000  1.0
  O  O16  1  0.500  0.000  0.500  1.0
  O  O17  1  0.000  0.500  0.500  1.0
  O  O18  1  0.286  0.786  0.000  1.0
  O  O19  1  0.714  0.214  0.000  1.0
  O  O20  1  0.214  0.286  0.000  1.0
  O  O21  1  0.786  0.714  0.000  1.0
  O  O22  1  0.157  0.504  0.000  1.0
  O  O23  1  0.843  0.496  0.000  1.0
  O  O24  1  0.343  0.004  0.000  1.0
  O  O25  1  0.657  0.996  0.000  1.0
  O  O26  1  0.504  0.843  0.000  1.0
  O  O27  1  0.496  0.157  0.000  1.0
  O  O28  1  0.004  0.657  0.000  1.0
  O  O29  1  0.996  0.343  0.000  1.0
  O  O30  1  0.432  0.698  0.500  1.0
  O  O31  1  0.568  0.302  0.500  1.0
  O  O32  1  0.068  0.198  0.500  1.0
  O  O33  1  0.932  0.802  0.500  1.0
  O  O34  1  0.698  0.568  0.500  1.0
  O  O35  1  0.302  0.432  0.500  1.0
  O  O36  1  0.198  0.932  0.500  1.0
  O  O37  1  0.802  0.068  0.500  1.0
  O  O38  1  0.565  0.632  0.000  1.0
  O  O39  1  0.435  0.368  0.000  1.0
  O  O40  1  0.935  0.132  0.000  1.0
  O  O41  1  0.065  0.868  0.000  1.0
  O  O42  1  0.632  0.435  0.000  1.0
  O  O43  1  0.368  0.565  0.000  1.0
  O  O44  1  0.132  0.065  0.000  1.0
  O  O45  1  0.868  0.935  0.000  1.0
[/CIF]
.