The material structure described by MgNbMnO4 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Nb(1)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, corners with four equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-72°. Nb(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, edges with four equivalent Mn(1)O6 octahedra, and edges with four equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-11°. Mn(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form distorted MnO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with four equivalent Nb(1)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-35°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), two equivalent Nb(1), and one Mn(1) atom to form a mixture of distorted edge and corner-sharing OMg2MnNb2 square pyramids. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1) and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Nb(1), and one Mn(1) atom to form a mixture of edge and corner-sharing OMg2MnNb2 trigonal bipyramids. In the fourth O site, O(4) is bonded in a square co-planar geometry to one Mg(1), one Nb(1), and two equivalent Mn(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgMnNbO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.635
_cell_length_b   5.635
_cell_length_c   5.635
_cell_angle_alpha   134.347
_cell_angle_beta   136.993
_cell_angle_gamma   64.515
_symmetry_Int_Tables_number   1
_cell_volume   86.069
_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  0.570  0.570  0.000  1.0
  Mn  Mn1  1  0.771  0.271  0.500  1.0
  Nb  Nb2  1  0.999  0.999  0.000  1.0
  O  O3  1  0.520  0.020  0.500  1.0
  O  O4  1  0.203  0.203  0.000  1.0
  O  O5  1  0.998  0.498  0.500  1.0
  O  O6  1  0.782  0.782  0.000  1.0
[/CIF]
.
The material structure described by MgNbMnO4 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(3) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Nb(1)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, corners with four equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-72°. Nb(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form NbO6 octahedra that share corners with four equivalent Nb(1)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, edges with four equivalent Mn(1)O6 octahedra, and edges with four equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-11°. Mn(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form distorted MnO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with four equivalent Nb(1)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-35°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), two equivalent Nb(1), and one Mn(1) atom to form a mixture of distorted edge and corner-sharing OMg2MnNb2 square pyramids. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1) and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Nb(1), and one Mn(1) atom to form a mixture of edge and corner-sharing OMg2MnNb2 trigonal bipyramids. In the fourth O site, O(4) is bonded in a square co-planar geometry to one Mg(1), one Nb(1), and two equivalent Mn(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgMnNbO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.635
_cell_length_b   5.635
_cell_length_c   5.635
_cell_angle_alpha   134.347
_cell_angle_beta   136.993
_cell_angle_gamma   64.515
_symmetry_Int_Tables_number   1
_cell_volume   86.069
_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  0.570  0.570  0.000  1.0
  Mn  Mn1  1  0.771  0.271  0.500  1.0
  Nb  Nb2  1  0.999  0.999  0.000  1.0
  O  O3  1  0.520  0.020  0.500  1.0
  O  O4  1  0.203  0.203  0.000  1.0
  O  O5  1  0.998  0.498  0.500  1.0
  O  O6  1  0.782  0.782  0.000  1.0
[/CIF]
.