The compound described by MgNd2Nb2O8 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(8) atom to form distorted MgO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a faceface with one Nb(1)O6 octahedra, and  a faceface with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-50°. 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(3), one O(5), one O(6), one O(7), and one O(8) atom. In the second Nd site, Nd(2) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, edges with two equivalent Nb(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Nb site, Nb(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Nd(1), one Nd(2), and one Nb(1) atom to form distorted ONd2MgNb tetrahedra that share  a cornercorner with one O(3)Nd2MgNb tetrahedra,  a cornercorner with one O(5)Nd2Nb2 tetrahedra, corners with three equivalent O(7)Nd2Nb2 tetrahedra,  an edgeedge with one O(3)Nd2MgNb tetrahedra, and  an edgeedge with one O(5)Nd2Nb2 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Nd(1), and one Nb(1) atom. In the third O site, O(3) is bonded to one Mg(1), one Nd(1), one Nd(2), and one Nb(2) atom to form distorted ONd2MgNb tetrahedra that share  a cornercorner with one O(1)Nd2MgNb tetrahedra,  a cornercorner with one O(7)Nd2Nb2 tetrahedra, corners with three equivalent O(5)Nd2Nb2 tetrahedra,  an edgeedge with one O(1)Nd2MgNb tetrahedra, and  an edgeedge with one O(7)Nd2Nb2 tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1), one Nd(2), and one Nb(2) atom. In the fifth O site, O(5) is bonded to one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom to form distorted ONd2Nb2 tetrahedra that share  a cornercorner with one O(1)Nd2MgNb tetrahedra, corners with three equivalent O(3)Nd2MgNb tetrahedra,  an edgeedge with one O(1)Nd2MgNb tetrahedra, and edges with two equivalent O(7)Nd2Nb2 tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Mg(1), one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom. In the seventh O site, O(7) is bonded to one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom to form distorted ONd2Nb2 tetrahedra that share  a cornercorner with one O(3)Nd2MgNb tetrahedra, corners with three equivalent O(1)Nd2MgNb tetrahedra,  an edgeedge with one O(3)Nd2MgNb tetrahedra, and edges with two equivalent O(5)Nd2Nb2 tetrahedra. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Mg(1), one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom. is represented by the CIF card [CIF]
data_Nd2MgNb2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.459
_cell_length_b   5.735
_cell_length_c   6.476
_cell_angle_alpha   113.029
_cell_angle_beta   99.273
_cell_angle_gamma   102.816
_symmetry_Int_Tables_number   1
_cell_volume   174.857
_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
  Nd  Nd0  1  0.159  0.395  0.767  1.0
  Nd  Nd1  1  0.859  0.658  0.266  1.0
  Mg  Mg2  1  0.512  0.031  0.512  1.0
  Nb  Nb3  1  0.688  0.944  0.900  1.0
  Nb  Nb4  1  0.324  0.107  0.127  1.0
  O  O5  1  0.831  0.983  0.624  1.0
  O  O6  1  0.380  0.719  0.649  1.0
  O  O7  1  0.184  0.070  0.407  1.0
  O  O8  1  0.632  0.333  0.381  1.0
  O  O9  1  0.038  0.292  0.083  1.0
  O  O10  1  0.507  0.802  0.124  1.0
  O  O11  1  0.977  0.760  0.947  1.0
  O  O12  1  0.510  0.252  0.907  1.0
[/CIF]
.
The compound described by MgNd2Nb2O8 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(8) atom to form distorted MgO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a faceface with one Nb(1)O6 octahedra, and  a faceface with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-50°. 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(3), one O(5), one O(6), one O(7), and one O(8) atom. In the second Nd site, Nd(2) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, edges with two equivalent Nb(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Nb site, Nb(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Nd(1), one Nd(2), and one Nb(1) atom to form distorted ONd2MgNb tetrahedra that share  a cornercorner with one O(3)Nd2MgNb tetrahedra,  a cornercorner with one O(5)Nd2Nb2 tetrahedra, corners with three equivalent O(7)Nd2Nb2 tetrahedra,  an edgeedge with one O(3)Nd2MgNb tetrahedra, and  an edgeedge with one O(5)Nd2Nb2 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Nd(1), and one Nb(1) atom. In the third O site, O(3) is bonded to one Mg(1), one Nd(1), one Nd(2), and one Nb(2) atom to form distorted ONd2MgNb tetrahedra that share  a cornercorner with one O(1)Nd2MgNb tetrahedra,  a cornercorner with one O(7)Nd2Nb2 tetrahedra, corners with three equivalent O(5)Nd2Nb2 tetrahedra,  an edgeedge with one O(1)Nd2MgNb tetrahedra, and  an edgeedge with one O(7)Nd2Nb2 tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1), one Nd(2), and one Nb(2) atom. In the fifth O site, O(5) is bonded to one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom to form distorted ONd2Nb2 tetrahedra that share  a cornercorner with one O(1)Nd2MgNb tetrahedra, corners with three equivalent O(3)Nd2MgNb tetrahedra,  an edgeedge with one O(1)Nd2MgNb tetrahedra, and edges with two equivalent O(7)Nd2Nb2 tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Mg(1), one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom. In the seventh O site, O(7) is bonded to one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom to form distorted ONd2Nb2 tetrahedra that share  a cornercorner with one O(3)Nd2MgNb tetrahedra, corners with three equivalent O(1)Nd2MgNb tetrahedra,  an edgeedge with one O(3)Nd2MgNb tetrahedra, and edges with two equivalent O(5)Nd2Nb2 tetrahedra. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Mg(1), one Nd(1), one Nd(2), one Nb(1), and one Nb(2) atom. is represented by the CIF card [CIF]
data_Nd2MgNb2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.459
_cell_length_b   5.735
_cell_length_c   6.476
_cell_angle_alpha   113.029
_cell_angle_beta   99.273
_cell_angle_gamma   102.816
_symmetry_Int_Tables_number   1
_cell_volume   174.857
_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
  Nd  Nd0  1  0.159  0.395  0.767  1.0
  Nd  Nd1  1  0.859  0.658  0.266  1.0
  Mg  Mg2  1  0.512  0.031  0.512  1.0
  Nb  Nb3  1  0.688  0.944  0.900  1.0
  Nb  Nb4  1  0.324  0.107  0.127  1.0
  O  O5  1  0.831  0.983  0.624  1.0
  O  O6  1  0.380  0.719  0.649  1.0
  O  O7  1  0.184  0.070  0.407  1.0
  O  O8  1  0.632  0.333  0.381  1.0
  O  O9  1  0.038  0.292  0.083  1.0
  O  O10  1  0.507  0.802  0.124  1.0
  O  O11  1  0.977  0.760  0.947  1.0
  O  O12  1  0.510  0.252  0.907  1.0
[/CIF]
.