The structure described by K2Na2MgPr2Nb2O10 crystallizes in the monoclinic Cm space group. K(1) is bonded in a 2-coordinate geometry to one O(1), one O(3), and one O(7) atom. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(2), one O(6), one O(8), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded to one O(3), one O(5), one O(7), and two equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Nb(1)O5 trigonal bipyramid and corners with four equivalent Nb(2)O5 trigonal bipyramids. Mg(1) is bonded in a distorted trigonal planar geometry to one O(6), one O(7), and one O(8) atom. Pr(1) is bonded in a 7-coordinate geometry to one O(2), one O(5), one O(8), two equivalent O(1), and two equivalent O(4) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(7), one O(8), and two equivalent O(4) atoms to form distorted NbO5 trigonal bipyramids that share  a cornercorner with one Na(2)O5 trigonal bipyramid. In the second Nb site, Nb(2) is bonded to one O(3), one O(5), one O(6), and two equivalent O(1) atoms to form NbO5 trigonal bipyramids that share corners with four equivalent Na(2)O5 trigonal bipyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one K(1), one Na(2), two equivalent Pr(1), and one Nb(2) atom. In the second O site, O(2) is bonded to one Na(1), two equivalent Pr(1), and one Nb(1) atom to form distorted ONaPr2Nb tetrahedra that share corners with two equivalent O(5)NaPr2Nb tetrahedra and corners with four equivalent O(8)NaPr2MgNb trigonal bipyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent K(1), one Na(2), and one Nb(2) atom. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to one Na(1), two equivalent Pr(1), and one Nb(1) atom. In the fifth O site, O(5) is bonded to one Na(2), two equivalent Pr(1), and one Nb(2) atom to form ONaPr2Nb tetrahedra that share corners with two equivalent O(2)NaPr2Nb tetrahedra and  an edgeedge with one O(8)NaPr2MgNb trigonal bipyramid. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(1), one Mg(1), and one Nb(2) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to two equivalent K(1), one Na(2), one Mg(1), and one Nb(1) atom. In the eighth O site, O(8) is bonded to one Na(1), one Mg(1), two equivalent Pr(1), and one Nb(1) atom to form a mixture of distorted corner and edge-sharing ONaPr2MgNb trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_K2Na2Pr2MgNb2O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.985
_cell_length_b   5.985
_cell_length_c   8.689
_cell_angle_alpha   90.205
_cell_angle_beta   89.795
_cell_angle_gamma   86.753
_symmetry_Int_Tables_number   1
_cell_volume   310.755
_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  0.751  0.137  0.047  1.0
  K  K1  1  0.363  0.749  0.047  1.0
  Na  Na2  1  0.286  0.214  0.742  1.0
  Na  Na3  1  0.751  0.749  0.280  1.0
  Pr  Pr4  1  0.213  0.730  0.515  1.0
  Pr  Pr5  1  0.770  0.287  0.515  1.0
  Mg  Mg6  1  0.000  0.500  0.911  1.0
  Nb  Nb7  1  0.707  0.793  0.714  1.0
  Nb  Nb8  1  0.245  0.255  0.260  1.0
  O  O9  1  0.459  0.465  0.342  1.0
  O  O10  1  0.508  0.992  0.594  1.0
  O  O11  1  0.476  0.024  0.252  1.0
  O  O12  1  0.510  0.543  0.677  1.0
  O  O13  1  0.013  0.487  0.351  1.0
  O  O14  1  0.191  0.309  0.041  1.0
  O  O15  1  0.777  0.723  0.954  1.0
  O  O16  1  0.035  0.041  0.342  1.0
  O  O17  1  0.997  0.503  0.693  1.0
  O  O18  1  0.957  0.990  0.677  1.0
[/CIF]
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The structure described by K2Na2MgPr2Nb2O10 crystallizes in the monoclinic Cm space group. K(1) is bonded in a 2-coordinate geometry to one O(1), one O(3), and one O(7) atom. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(2), one O(6), one O(8), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded to one O(3), one O(5), one O(7), and two equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Nb(1)O5 trigonal bipyramid and corners with four equivalent Nb(2)O5 trigonal bipyramids. Mg(1) is bonded in a distorted trigonal planar geometry to one O(6), one O(7), and one O(8) atom. Pr(1) is bonded in a 7-coordinate geometry to one O(2), one O(5), one O(8), two equivalent O(1), and two equivalent O(4) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(7), one O(8), and two equivalent O(4) atoms to form distorted NbO5 trigonal bipyramids that share  a cornercorner with one Na(2)O5 trigonal bipyramid. In the second Nb site, Nb(2) is bonded to one O(3), one O(5), one O(6), and two equivalent O(1) atoms to form NbO5 trigonal bipyramids that share corners with four equivalent Na(2)O5 trigonal bipyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one K(1), one Na(2), two equivalent Pr(1), and one Nb(2) atom. In the second O site, O(2) is bonded to one Na(1), two equivalent Pr(1), and one Nb(1) atom to form distorted ONaPr2Nb tetrahedra that share corners with two equivalent O(5)NaPr2Nb tetrahedra and corners with four equivalent O(8)NaPr2MgNb trigonal bipyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent K(1), one Na(2), and one Nb(2) atom. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to one Na(1), two equivalent Pr(1), and one Nb(1) atom. In the fifth O site, O(5) is bonded to one Na(2), two equivalent Pr(1), and one Nb(2) atom to form ONaPr2Nb tetrahedra that share corners with two equivalent O(2)NaPr2Nb tetrahedra and  an edgeedge with one O(8)NaPr2MgNb trigonal bipyramid. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(1), one Mg(1), and one Nb(2) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to two equivalent K(1), one Na(2), one Mg(1), and one Nb(1) atom. In the eighth O site, O(8) is bonded to one Na(1), one Mg(1), two equivalent Pr(1), and one Nb(1) atom to form a mixture of distorted corner and edge-sharing ONaPr2MgNb trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_K2Na2Pr2MgNb2O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.985
_cell_length_b   5.985
_cell_length_c   8.689
_cell_angle_alpha   90.205
_cell_angle_beta   89.795
_cell_angle_gamma   86.753
_symmetry_Int_Tables_number   1
_cell_volume   310.755
_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  0.751  0.137  0.047  1.0
  K  K1  1  0.363  0.749  0.047  1.0
  Na  Na2  1  0.286  0.214  0.742  1.0
  Na  Na3  1  0.751  0.749  0.280  1.0
  Pr  Pr4  1  0.213  0.730  0.515  1.0
  Pr  Pr5  1  0.770  0.287  0.515  1.0
  Mg  Mg6  1  0.000  0.500  0.911  1.0
  Nb  Nb7  1  0.707  0.793  0.714  1.0
  Nb  Nb8  1  0.245  0.255  0.260  1.0
  O  O9  1  0.459  0.465  0.342  1.0
  O  O10  1  0.508  0.992  0.594  1.0
  O  O11  1  0.476  0.024  0.252  1.0
  O  O12  1  0.510  0.543  0.677  1.0
  O  O13  1  0.013  0.487  0.351  1.0
  O  O14  1  0.191  0.309  0.041  1.0
  O  O15  1  0.777  0.723  0.954  1.0
  O  O16  1  0.035  0.041  0.342  1.0
  O  O17  1  0.997  0.503  0.693  1.0
  O  O18  1  0.957  0.990  0.677  1.0
[/CIF]
.