The structure described by MgNb4O10 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(3), one O(6), one O(7), and two equivalent O(4) atoms to form distorted corner-sharing MgO5 trigonal bipyramids. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(8), and two equivalent O(1) atoms. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms. 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 distorted ONb4 trigonal pyramids that share corners with two equivalent O(4)Mg2Nb2 tetrahedra,  a cornercorner with one O(3)MgNb3 trigonal pyramid, corners with two equivalent O(1)Nb4 trigonal pyramids, and edges with two equivalent O(10)Nb4 trigonal pyramids. In the second O site, O(2) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the third O site, O(3) is bonded to one Mg(1), one Nb(4), and two equivalent Nb(2) atoms to form distorted OMgNb3 trigonal pyramids that share  a cornercorner with one O(1)Nb4 trigonal pyramid, corners with two equivalent O(3)MgNb3 trigonal pyramids, edges with two equivalent O(4)Mg2Nb2 tetrahedra, and edges with two equivalent O(10)Nb4 trigonal pyramids. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Nb(1), and one Nb(2) atom to form OMg2Nb2 tetrahedra that share corners with two equivalent O(4)Mg2Nb2 tetrahedra, corners with two equivalent O(1)Nb4 trigonal pyramids,  an edgeedge with one O(10)Nb4 trigonal pyramid, and edges with two equivalent O(3)MgNb3 trigonal pyramids. In the fifth O site, O(5) is bonded in a single-bond geometry to one Nb(2) atom. In the sixth O site, O(6) is bonded in a water-like geometry to one Mg(1) and one Nb(3) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Mg(1), 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 distorted ONb4 trigonal pyramids that share corners with two equivalent O(10)Nb4 trigonal pyramids,  an edgeedge with one O(4)Mg2Nb2 tetrahedra, edges with two equivalent O(3)MgNb3 trigonal pyramids, and edges with two equivalent O(1)Nb4 trigonal pyramids. is represented by the CIF card [CIF]
data_MgNb4O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.356
_cell_length_b   3.974
_cell_length_c   6.894
_cell_angle_alpha   90.000
_cell_angle_beta   91.056
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   201.480
_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  0.750  0.986  1.0
  Nb  Nb1  1  0.084  0.250  0.816  1.0
  Nb  Nb2  1  0.276  0.250  0.299  1.0
  Nb  Nb3  1  0.730  0.750  0.707  1.0
  Nb  Nb4  1  0.906  0.750  0.183  1.0
  O  O5  1  0.034  0.750  0.856  1.0
  O  O6  1  0.174  0.250  0.567  1.0
  O  O7  1  0.210  0.750  0.242  1.0
  O  O8  1  0.312  0.250  0.986  1.0
  O  O9  1  0.512  0.250  0.338  1.0
  O  O10  1  0.486  0.750  0.701  1.0
  O  O11  1  0.694  0.750  0.021  1.0
  O  O12  1  0.807  0.250  0.741  1.0
  O  O13  1  0.825  0.750  0.436  1.0
  O  O14  1  0.973  0.250  0.149  1.0
[/CIF]
.
The structure described by MgNb4O10 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(3), one O(6), one O(7), and two equivalent O(4) atoms to form distorted corner-sharing MgO5 trigonal bipyramids. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(8), and two equivalent O(1) atoms. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms. 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 distorted ONb4 trigonal pyramids that share corners with two equivalent O(4)Mg2Nb2 tetrahedra,  a cornercorner with one O(3)MgNb3 trigonal pyramid, corners with two equivalent O(1)Nb4 trigonal pyramids, and edges with two equivalent O(10)Nb4 trigonal pyramids. In the second O site, O(2) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the third O site, O(3) is bonded to one Mg(1), one Nb(4), and two equivalent Nb(2) atoms to form distorted OMgNb3 trigonal pyramids that share  a cornercorner with one O(1)Nb4 trigonal pyramid, corners with two equivalent O(3)MgNb3 trigonal pyramids, edges with two equivalent O(4)Mg2Nb2 tetrahedra, and edges with two equivalent O(10)Nb4 trigonal pyramids. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Nb(1), and one Nb(2) atom to form OMg2Nb2 tetrahedra that share corners with two equivalent O(4)Mg2Nb2 tetrahedra, corners with two equivalent O(1)Nb4 trigonal pyramids,  an edgeedge with one O(10)Nb4 trigonal pyramid, and edges with two equivalent O(3)MgNb3 trigonal pyramids. In the fifth O site, O(5) is bonded in a single-bond geometry to one Nb(2) atom. In the sixth O site, O(6) is bonded in a water-like geometry to one Mg(1) and one Nb(3) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Mg(1), 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 distorted ONb4 trigonal pyramids that share corners with two equivalent O(10)Nb4 trigonal pyramids,  an edgeedge with one O(4)Mg2Nb2 tetrahedra, edges with two equivalent O(3)MgNb3 trigonal pyramids, and edges with two equivalent O(1)Nb4 trigonal pyramids. is represented by the CIF card [CIF]
data_MgNb4O10
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.356
_cell_length_b   3.974
_cell_length_c   6.894
_cell_angle_alpha   90.000
_cell_angle_beta   91.056
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   201.480
_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  0.750  0.986  1.0
  Nb  Nb1  1  0.084  0.250  0.816  1.0
  Nb  Nb2  1  0.276  0.250  0.299  1.0
  Nb  Nb3  1  0.730  0.750  0.707  1.0
  Nb  Nb4  1  0.906  0.750  0.183  1.0
  O  O5  1  0.034  0.750  0.856  1.0
  O  O6  1  0.174  0.250  0.567  1.0
  O  O7  1  0.210  0.750  0.242  1.0
  O  O8  1  0.312  0.250  0.986  1.0
  O  O9  1  0.512  0.250  0.338  1.0
  O  O10  1  0.486  0.750  0.701  1.0
  O  O11  1  0.694  0.750  0.021  1.0
  O  O12  1  0.807  0.250  0.741  1.0
  O  O13  1  0.825  0.750  0.436  1.0
  O  O14  1  0.973  0.250  0.149  1.0
[/CIF]
.