The material described by MgNb4(NiO6)2 crystallizes in the monoclinic P2/m space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, edges with four equivalent Nb(2)O6 octahedra, and faces with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, corners with four equivalent Ni(2)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-56°. In the second Nb site, Nb(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, corners with four equivalent Ni(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-56°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form NiO6 octahedra that share corners with eight equivalent Nb(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and faces with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-52°. In the second Ni site, Ni(2) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form NiO6 octahedra that share corners with eight equivalent Nb(1)O6 octahedra and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Ni(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Nb(1) and one Ni(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Nb(1), one Nb(2), and one Ni(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Nb(2), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing OMgNb2Ni trigonal pyramids. is represented by the CIF card [CIF]
data_MgNb4(NiO6)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.870
_cell_length_b   4.974
_cell_length_c   9.034
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.032
_symmetry_Int_Tables_number   1
_cell_volume   218.849
_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
  Mg  Mg0  1  0.500  0.000  0.670  1.0
  Nb  Nb1  1  0.000  0.000  0.021  1.0
  Nb  Nb2  1  0.000  0.000  0.320  1.0
  Nb  Nb3  1  0.500  0.500  0.852  1.0
  Nb  Nb4  1  0.500  0.500  0.488  1.0
  Ni  Ni5  1  0.000  0.000  0.670  1.0
  Ni  Ni6  1  0.500  0.500  0.170  1.0
  O  O7  1  0.242  0.822  0.831  1.0
  O  O8  1  0.228  0.796  0.171  1.0
  O  O9  1  0.242  0.822  0.509  1.0
  O  O10  1  0.273  0.309  0.996  1.0
  O  O11  1  0.273  0.309  0.344  1.0
  O  O12  1  0.292  0.332  0.670  1.0
  O  O13  1  0.727  0.691  0.996  1.0
  O  O14  1  0.727  0.691  0.344  1.0
  O  O15  1  0.708  0.668  0.670  1.0
  O  O16  1  0.758  0.178  0.831  1.0
  O  O17  1  0.772  0.204  0.171  1.0
  O  O18  1  0.758  0.178  0.509  1.0
[/CIF]
.
The material described by MgNb4(NiO6)2 crystallizes in the monoclinic P2/m space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, edges with four equivalent Nb(2)O6 octahedra, and faces with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, corners with four equivalent Ni(2)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-56°. In the second Nb site, Nb(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra, corners with four equivalent Ni(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-56°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form NiO6 octahedra that share corners with eight equivalent Nb(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and faces with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-52°. In the second Ni site, Ni(2) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form NiO6 octahedra that share corners with eight equivalent Nb(1)O6 octahedra and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Ni(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Nb(1) and one Ni(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Nb(1), one Nb(2), and one Ni(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Nb(2), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing OMgNb2Ni trigonal pyramids. is represented by the CIF card [CIF]
data_MgNb4(NiO6)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.870
_cell_length_b   4.974
_cell_length_c   9.034
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.032
_symmetry_Int_Tables_number   1
_cell_volume   218.849
_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
  Mg  Mg0  1  0.500  0.000  0.670  1.0
  Nb  Nb1  1  0.000  0.000  0.021  1.0
  Nb  Nb2  1  0.000  0.000  0.320  1.0
  Nb  Nb3  1  0.500  0.500  0.852  1.0
  Nb  Nb4  1  0.500  0.500  0.488  1.0
  Ni  Ni5  1  0.000  0.000  0.670  1.0
  Ni  Ni6  1  0.500  0.500  0.170  1.0
  O  O7  1  0.242  0.822  0.831  1.0
  O  O8  1  0.228  0.796  0.171  1.0
  O  O9  1  0.242  0.822  0.509  1.0
  O  O10  1  0.273  0.309  0.996  1.0
  O  O11  1  0.273  0.309  0.344  1.0
  O  O12  1  0.292  0.332  0.670  1.0
  O  O13  1  0.727  0.691  0.996  1.0
  O  O14  1  0.727  0.691  0.344  1.0
  O  O15  1  0.708  0.668  0.670  1.0
  O  O16  1  0.758  0.178  0.831  1.0
  O  O17  1  0.772  0.204  0.171  1.0
  O  O18  1  0.758  0.178  0.509  1.0
[/CIF]
.