The structure described by MgNb4O10 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(2), one O(4), one O(5), and two equivalent O(6) atoms to form MgO5 trigonal bipyramids that share  a cornercorner with one Nb(2)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 29°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(2), one O(4), one O(8), and two equivalent O(1) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 8-25°. In the second Nb site, Nb(2) is bonded to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 8-36°. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(1), one O(6), one O(7), one O(9), and two equivalent O(8) atoms. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(7), one O(9), and two equivalent O(10) atoms. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Nb(3), one Nb(4), and two equivalent Nb(1) atoms to form a mixture of distorted corner and edge-sharing ONb4 trigonal pyramids. In the second O site, O(2) is bonded in a T-shaped geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Nb(4) and two equivalent Nb(2) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the fifth O site, O(5) is bonded in a water-like geometry to one Mg(1) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Mg(1) and one Nb(3) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Nb(3) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1) and two equivalent Nb(3) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the tenth O site, O(10) is bonded to one Nb(1), one Nb(2), and two equivalent Nb(4) atoms to form a mixture of distorted corner and edge-sharing ONb4 trigonal pyramids. is represented by the CIF file [CIF]
data_MgNb4O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.308
_cell_length_b   3.932
_cell_length_c   6.611
_cell_angle_alpha   90.000
_cell_angle_beta   87.618
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   215.806
_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  0.418  0.250  0.664  1.0
  Nb  Nb1  1  0.069  0.250  0.817  1.0
  Nb  Nb2  1  0.261  0.250  0.257  1.0
  Nb  Nb3  1  0.741  0.750  0.738  1.0
  Nb  Nb4  1  0.924  0.750  0.192  1.0
  O  O5  1  0.016  0.750  0.829  1.0
  O  O6  1  0.178  0.250  0.554  1.0
  O  O7  1  0.189  0.750  0.233  1.0
  O  O8  1  0.281  0.250  0.935  1.0
  O  O9  1  0.460  0.250  0.354  1.0
  O  O10  1  0.520  0.750  0.698  1.0
  O  O11  1  0.737  0.750  0.043  1.0
  O  O12  1  0.810  0.250  0.752  1.0
  O  O13  1  0.838  0.750  0.454  1.0
  O  O14  1  0.990  0.250  0.156  1.0
[/CIF]
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The structure described by MgNb4O10 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(2), one O(4), one O(5), and two equivalent O(6) atoms to form MgO5 trigonal bipyramids that share  a cornercorner with one Nb(2)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 29°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(2), one O(4), one O(8), and two equivalent O(1) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 8-25°. In the second Nb site, Nb(2) is bonded to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  an edgeedge with one Nb(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 8-36°. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(1), one O(6), one O(7), one O(9), and two equivalent O(8) atoms. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(7), one O(9), and two equivalent O(10) atoms. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Nb(3), one Nb(4), and two equivalent Nb(1) atoms to form a mixture of distorted corner and edge-sharing ONb4 trigonal pyramids. In the second O site, O(2) is bonded in a T-shaped geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Nb(4) and two equivalent Nb(2) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1), one Nb(1), and one Nb(2) atom. In the fifth O site, O(5) is bonded in a water-like geometry to one Mg(1) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Mg(1) and one Nb(3) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Nb(3) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1) and two equivalent Nb(3) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the tenth O site, O(10) is bonded to one Nb(1), one Nb(2), and two equivalent Nb(4) atoms to form a mixture of distorted corner and edge-sharing ONb4 trigonal pyramids. is represented by the CIF file [CIF]
data_MgNb4O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.308
_cell_length_b   3.932
_cell_length_c   6.611
_cell_angle_alpha   90.000
_cell_angle_beta   87.618
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   215.806
_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  0.418  0.250  0.664  1.0
  Nb  Nb1  1  0.069  0.250  0.817  1.0
  Nb  Nb2  1  0.261  0.250  0.257  1.0
  Nb  Nb3  1  0.741  0.750  0.738  1.0
  Nb  Nb4  1  0.924  0.750  0.192  1.0
  O  O5  1  0.016  0.750  0.829  1.0
  O  O6  1  0.178  0.250  0.554  1.0
  O  O7  1  0.189  0.750  0.233  1.0
  O  O8  1  0.281  0.250  0.935  1.0
  O  O9  1  0.460  0.250  0.354  1.0
  O  O10  1  0.520  0.750  0.698  1.0
  O  O11  1  0.737  0.750  0.043  1.0
  O  O12  1  0.810  0.250  0.752  1.0
  O  O13  1  0.838  0.750  0.454  1.0
  O  O14  1  0.990  0.250  0.156  1.0
[/CIF]
.