The crystal structure described by K2Na2MgNd2Nb2O10 crystallizes in the triclinic P1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 2-coordinate geometry to one O(10), one O(3), and one O(9) atom. In the second K site, K(2) is bonded in a 2-coordinate geometry to one O(10), one O(3), and one O(5) atom. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(6), one O(7), and one O(8) atom. In the second Na site, Na(2) is bonded to one O(10), one O(3), one O(4), one O(5), and one O(9) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Nb(2)O5 trigonal bipyramid and corners with four equivalent Nb(1)O5 trigonal bipyramids. Mg(1) is bonded in a distorted trigonal planar geometry to one O(3), one O(6), and one O(7) atom. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. In the second Nd site, Nd(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(4), one O(5), one O(6), and one O(9) atom to form NbO5 trigonal bipyramids that share corners with four equivalent Na(2)O5 trigonal bipyramids. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(3), one O(7), and one O(8) atom to form distorted NbO5 trigonal bipyramids that share  a cornercorner with one Na(2)O5 trigonal bipyramid. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted see-saw-like geometry to one Na(1), one Nd(1), one Nd(2), and one Nb(2) atom. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Na(1), one Nd(1), one Nd(2), and one Nb(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one K(1), one K(2), one Na(2), one Mg(1), and one Nb(2) atom. In the fourth O site, O(4) is bonded to one Na(2), one Nd(1), one Nd(2), and one Nb(1) atom to form ONaNd2Nb tetrahedra that share corners with two equivalent O(8)NaNd2Nb tetrahedra and  an edgeedge with one O(7)NaNd2MgNb trigonal bipyramid. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one K(2), one Na(2), one Nd(1), one Nd(2), and one Nb(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(1), one Mg(1), and one Nb(1) atom. In the seventh O site, O(7) is bonded to one Na(1), one Mg(1), one Nd(1), one Nd(2), and one Nb(2) atom to form a mixture of distorted corner and edge-sharing ONaNd2MgNb trigonal bipyramids. In the eighth O site, O(8) is bonded to one Na(1), one Nd(1), one Nd(2), and one Nb(2) atom to form distorted ONaNd2Nb tetrahedra that share corners with two equivalent O(4)NaNd2Nb tetrahedra and corners with four equivalent O(7)NaNd2MgNb trigonal bipyramids. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one K(1), one Na(2), one Nd(1), one Nd(2), and one Nb(1) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Na(2), and one Nb(1) atom. is represented by the CIF file [CIF]
data_K2Na2Nd2MgNb2O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.954
_cell_length_b   5.952
_cell_length_c   8.723
_cell_angle_alpha   89.669
_cell_angle_beta   89.903
_cell_angle_gamma   86.695
_symmetry_Int_Tables_number   1
_cell_volume   308.595
_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  0.141  0.748  0.042  1.0
  K  K1  1  0.753  0.363  0.049  1.0
  Na  Na2  1  0.211  0.285  0.737  1.0
  Na  Na3  1  0.750  0.753  0.281  1.0
  Nd  Nd4  1  0.286  0.770  0.516  1.0
  Nd  Nd5  1  0.729  0.212  0.516  1.0
  Mg  Mg6  1  0.502  0.007  0.909  1.0
  Nb  Nb7  1  0.255  0.246  0.262  1.0
  Nb  Nb8  1  0.791  0.706  0.713  1.0
  O  O9  1  0.989  0.957  0.674  1.0
  O  O10  1  0.540  0.509  0.675  1.0
  O  O11  1  0.722  0.778  0.952  1.0
  O  O12  1  0.488  0.013  0.355  1.0
  O  O13  1  0.467  0.461  0.344  1.0
  O  O14  1  0.311  0.191  0.044  1.0
  O  O15  1  0.501  0.997  0.691  1.0
  O  O16  1  0.990  0.509  0.589  1.0
  O  O17  1  0.039  0.036  0.344  1.0
  O  O18  1  0.026  0.480  0.252  1.0
[/CIF]
.
The crystal structure described by K2Na2MgNd2Nb2O10 crystallizes in the triclinic P1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 2-coordinate geometry to one O(10), one O(3), and one O(9) atom. In the second K site, K(2) is bonded in a 2-coordinate geometry to one O(10), one O(3), and one O(5) atom. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(6), one O(7), and one O(8) atom. In the second Na site, Na(2) is bonded to one O(10), one O(3), one O(4), one O(5), and one O(9) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Nb(2)O5 trigonal bipyramid and corners with four equivalent Nb(1)O5 trigonal bipyramids. Mg(1) is bonded in a distorted trigonal planar geometry to one O(3), one O(6), and one O(7) atom. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. In the second Nd site, Nd(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(4), one O(5), one O(6), and one O(9) atom to form NbO5 trigonal bipyramids that share corners with four equivalent Na(2)O5 trigonal bipyramids. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(3), one O(7), and one O(8) atom to form distorted NbO5 trigonal bipyramids that share  a cornercorner with one Na(2)O5 trigonal bipyramid. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted see-saw-like geometry to one Na(1), one Nd(1), one Nd(2), and one Nb(2) atom. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Na(1), one Nd(1), one Nd(2), and one Nb(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one K(1), one K(2), one Na(2), one Mg(1), and one Nb(2) atom. In the fourth O site, O(4) is bonded to one Na(2), one Nd(1), one Nd(2), and one Nb(1) atom to form ONaNd2Nb tetrahedra that share corners with two equivalent O(8)NaNd2Nb tetrahedra and  an edgeedge with one O(7)NaNd2MgNb trigonal bipyramid. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one K(2), one Na(2), one Nd(1), one Nd(2), and one Nb(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(1), one Mg(1), and one Nb(1) atom. In the seventh O site, O(7) is bonded to one Na(1), one Mg(1), one Nd(1), one Nd(2), and one Nb(2) atom to form a mixture of distorted corner and edge-sharing ONaNd2MgNb trigonal bipyramids. In the eighth O site, O(8) is bonded to one Na(1), one Nd(1), one Nd(2), and one Nb(2) atom to form distorted ONaNd2Nb tetrahedra that share corners with two equivalent O(4)NaNd2Nb tetrahedra and corners with four equivalent O(7)NaNd2MgNb trigonal bipyramids. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one K(1), one Na(2), one Nd(1), one Nd(2), and one Nb(1) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Na(2), and one Nb(1) atom. is represented by the CIF file [CIF]
data_K2Na2Nd2MgNb2O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.954
_cell_length_b   5.952
_cell_length_c   8.723
_cell_angle_alpha   89.669
_cell_angle_beta   89.903
_cell_angle_gamma   86.695
_symmetry_Int_Tables_number   1
_cell_volume   308.595
_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  0.141  0.748  0.042  1.0
  K  K1  1  0.753  0.363  0.049  1.0
  Na  Na2  1  0.211  0.285  0.737  1.0
  Na  Na3  1  0.750  0.753  0.281  1.0
  Nd  Nd4  1  0.286  0.770  0.516  1.0
  Nd  Nd5  1  0.729  0.212  0.516  1.0
  Mg  Mg6  1  0.502  0.007  0.909  1.0
  Nb  Nb7  1  0.255  0.246  0.262  1.0
  Nb  Nb8  1  0.791  0.706  0.713  1.0
  O  O9  1  0.989  0.957  0.674  1.0
  O  O10  1  0.540  0.509  0.675  1.0
  O  O11  1  0.722  0.778  0.952  1.0
  O  O12  1  0.488  0.013  0.355  1.0
  O  O13  1  0.467  0.461  0.344  1.0
  O  O14  1  0.311  0.191  0.044  1.0
  O  O15  1  0.501  0.997  0.691  1.0
  O  O16  1  0.990  0.509  0.589  1.0
  O  O17  1  0.039  0.036  0.344  1.0
  O  O18  1  0.026  0.480  0.252  1.0
[/CIF]
.