MgNb3O7F crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Nb(1)O6 octahedra, edges with two equivalent Nb(2)O6F pentagonal bipyramids, and edges with two equivalent Nb(3)O6F pentagonal bipyramids. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(6), one O(7), and two equivalent O(3) atoms to form distorted NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6F pentagonal bipyramids, corners with two equivalent Nb(3)O6F pentagonal bipyramids,  an edgeedge with one Nb(2)O6F pentagonal bipyramid,  an edgeedge with one Nb(3)O6F pentagonal bipyramid, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 18°. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(6), one O(7), two equivalent O(4), and one F(1) atom to form NbO6F pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Nb(3)O6F pentagonal bipyramid, corners with two equivalent Nb(2)O6F pentagonal bipyramids,  an edgeedge with one Nb(1)O6 octahedra, edges with two equivalent Nb(3)O6F pentagonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 35-43°. In the third Nb site, Nb(3) is bonded to one O(1), one O(2), one O(6), one O(7), two equivalent O(5), and one F(1) atom to form NbO6F pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6F pentagonal bipyramid, corners with two equivalent Nb(3)O6F pentagonal bipyramids,  an edgeedge with one Nb(1)O6 octahedra, edges with two equivalent Nb(2)O6F pentagonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 34-41°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), one Nb(1), one Nb(2), and one Nb(3) atom to form corner-sharing OMg2Nb3 trigonal bipyramids. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(2) atoms. In the fifth O site, O(5) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(3) atoms. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Nb(3) atom. F(1) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom.
MgNb3O7F crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Nb(1)O6 octahedra, edges with two equivalent Nb(2)O6F pentagonal bipyramids, and edges with two equivalent Nb(3)O6F pentagonal bipyramids. The Mg(1)-O(3) bond length is 1.99 Å. The Mg(1)-O(4) bond length is 2.01 Å. The Mg(1)-O(5) bond length is 2.07 Å. Both Mg(1)-O(1) bond lengths are 2.00 Å. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(6), one O(7), and two equivalent O(3) atoms to form distorted NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6F pentagonal bipyramids, corners with two equivalent Nb(3)O6F pentagonal bipyramids,  an edgeedge with one Nb(2)O6F pentagonal bipyramid,  an edgeedge with one Nb(3)O6F pentagonal bipyramid, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 18°. The Nb(1)-O(1) bond length is 2.27 Å. The Nb(1)-O(2) bond length is 2.09 Å. The Nb(1)-O(6) bond length is 1.95 Å. The Nb(1)-O(7) bond length is 2.09 Å. Both Nb(1)-O(3) bond lengths are 2.03 Å. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(6), one O(7), two equivalent O(4), and one F(1) atom to form NbO6F pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Nb(3)O6F pentagonal bipyramid, corners with two equivalent Nb(2)O6F pentagonal bipyramids,  an edgeedge with one Nb(1)O6 octahedra, edges with two equivalent Nb(3)O6F pentagonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 35-43°. The Nb(2)-O(1) bond length is 2.27 Å. The Nb(2)-O(2) bond length is 2.05 Å. The Nb(2)-O(6) bond length is 2.22 Å. The Nb(2)-O(7) bond length is 2.01 Å. Both Nb(2)-O(4) bond lengths are 2.02 Å. The Nb(2)-F(1) bond length is 2.23 Å. In the third Nb site, Nb(3) is bonded to one O(1), one O(2), one O(6), one O(7), two equivalent O(5), and one F(1) atom to form NbO6F pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6F pentagonal bipyramid, corners with two equivalent Nb(3)O6F pentagonal bipyramids,  an edgeedge with one Nb(1)O6 octahedra, edges with two equivalent Nb(2)O6F pentagonal bipyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 34-41°. The Nb(3)-O(1) bond length is 2.27 Å. The Nb(3)-O(2) bond length is 2.05 Å. The Nb(3)-O(6) bond length is 2.15 Å. The Nb(3)-O(7) bond length is 2.14 Å. Both Nb(3)-O(5) bond lengths are 2.01 Å. The Nb(3)-F(1) bond length is 2.16 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), one Nb(1), one Nb(2), and one Nb(3) atom to form corner-sharing OMg2Nb3 trigonal bipyramids. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(2) atoms. In the fifth O site, O(5) is bonded in a T-shaped geometry to one Mg(1) and two equivalent Nb(3) atoms. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Nb(1), one Nb(2), and one Nb(3) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Nb(1), one Nb(2), and one Nb(3) atom. F(1) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom.