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.
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°. The Mg(1)-O(2) bond length is 2.15 Å. The Mg(1)-O(4) bond length is 2.08 Å. The Mg(1)-O(5) bond length is 2.07 Å. Both Mg(1)-O(6) bond lengths are 2.16 Å. 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°. The Nb(1)-O(10) bond length is 2.31 Å. The Nb(1)-O(2) bond length is 1.93 Å. The Nb(1)-O(4) bond length is 1.96 Å. The Nb(1)-O(8) bond length is 2.21 Å. Both Nb(1)-O(1) bond lengths are 2.01 Å. 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°. The Nb(2)-O(10) bond length is 2.38 Å. The Nb(2)-O(2) bond length is 2.05 Å. The Nb(2)-O(4) bond length is 2.13 Å. The Nb(2)-O(5) bond length is 1.80 Å. Both Nb(2)-O(3) bond lengths are 2.06 Å. 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. The Nb(3)-O(1) bond length is 2.39 Å. The Nb(3)-O(6) bond length is 1.87 Å. The Nb(3)-O(7) bond length is 2.02 Å. The Nb(3)-O(9) bond length is 2.01 Å. Both Nb(3)-O(8) bond lengths are 2.05 Å. 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. The Nb(4)-O(1) bond length is 2.49 Å. The Nb(4)-O(3) bond length is 2.22 Å. The Nb(4)-O(7) bond length is 1.87 Å. The Nb(4)-O(9) bond length is 1.85 Å. Both Nb(4)-O(10) bond lengths are 2.05 Å. 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.