Na4MgV2O6 crystallizes in the monoclinic Cm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with three equivalent V(1)O5 trigonal bipyramids, corners with five equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O5 trigonal bipyramid, and edges with two equivalent V(2)O5 trigonal bipyramids. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. Mg(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one V(1)O5 trigonal bipyramid,  a cornercorner with one V(2)O5 trigonal bipyramid, corners with four equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one V(2)O5 trigonal bipyramid, edges with two equivalent Na(1)O5 trigonal bipyramids, and  a faceface with one V(1)O5 trigonal bipyramid. There are two inequivalent V sites. In the first V site, V(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(3) atoms to form distorted VO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent V(1)O5 trigonal bipyramids, corners with six equivalent Na(1)O5 trigonal bipyramids, edges with two equivalent V(2)O5 trigonal bipyramids, and  a faceface with one Mg(1)O5 trigonal bipyramid. In the second V site, V(2) is bonded to one O(3), two equivalent O(2), and two equivalent O(4) atoms to form VO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent V(2)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O5 trigonal bipyramid, edges with two equivalent V(1)O5 trigonal bipyramids, and edges with four equivalent Na(1)O5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), two equivalent Na(2), one Mg(1), and one V(1) atom to form distorted ONa4MgV pentagonal pyramids that share corners with four equivalent O(1)Na4MgV pentagonal pyramids, corners with three equivalent O(4)Na2V3 trigonal bipyramids,  an edgeedge with one O(3)Na2MgV3 octahedra,  an edgeedge with one O(1)Na4MgV pentagonal pyramid, and  a faceface with one O(3)Na2MgV3 octahedra. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), one Mg(1), and one V(2) atom. In the third O site, O(3) is bonded to two equivalent Na(2), one Mg(1), one V(2), and two equivalent V(1) atoms to form distorted ONa2MgV3 octahedra that share corners with two equivalent O(3)Na2MgV3 octahedra, edges with two equivalent O(1)Na4MgV pentagonal pyramids, edges with two equivalent O(4)Na2V3 trigonal bipyramids, and faces with two equivalent O(1)Na4MgV pentagonal pyramids. The corner-sharing octahedral tilt angles are 2°. In the fourth O site, O(4) is bonded to two equivalent Na(1), one V(1), and two equivalent V(2) atoms to form ONa2V3 trigonal bipyramids that share corners with six equivalent O(1)Na4MgV pentagonal pyramids, corners with two equivalent O(4)Na2V3 trigonal bipyramids, and edges with two equivalent O(3)Na2MgV3 octahedra.
Na4MgV2O6 crystallizes in the monoclinic Cm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with three equivalent V(1)O5 trigonal bipyramids, corners with five equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O5 trigonal bipyramid, and edges with two equivalent V(2)O5 trigonal bipyramids. The Na(1)-O(4) bond length is 2.41 Å. There is one shorter (2.35 Å) and one longer (2.50 Å) Na(1)-O(1) bond length. There is one shorter (2.30 Å) and one longer (2.37 Å) Na(1)-O(2) bond length. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. The Na(2)-O(3) bond length is 2.52 Å. There is one shorter (2.36 Å) and one longer (2.42 Å) Na(2)-O(1) bond length. There is one shorter (2.31 Å) and one longer (2.48 Å) Na(2)-O(2) bond length. Mg(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one V(1)O5 trigonal bipyramid,  a cornercorner with one V(2)O5 trigonal bipyramid, corners with four equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one V(2)O5 trigonal bipyramid, edges with two equivalent Na(1)O5 trigonal bipyramids, and  a faceface with one V(1)O5 trigonal bipyramid. The Mg(1)-O(3) bond length is 2.22 Å. Both Mg(1)-O(1) bond lengths are 2.19 Å. Both Mg(1)-O(2) bond lengths are 2.08 Å. There are two inequivalent V sites. In the first V site, V(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(3) atoms to form distorted VO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent V(1)O5 trigonal bipyramids, corners with six equivalent Na(1)O5 trigonal bipyramids, edges with two equivalent V(2)O5 trigonal bipyramids, and  a faceface with one Mg(1)O5 trigonal bipyramid. The V(1)-O(4) bond length is 1.92 Å. Both V(1)-O(1) bond lengths are 1.92 Å. There is one shorter (2.12 Å) and one longer (2.41 Å) V(1)-O(3) bond length. In the second V site, V(2) is bonded to one O(3), two equivalent O(2), and two equivalent O(4) atoms to form VO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent V(2)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O5 trigonal bipyramid, edges with two equivalent V(1)O5 trigonal bipyramids, and edges with four equivalent Na(1)O5 trigonal bipyramids. The V(2)-O(3) bond length is 2.02 Å. Both V(2)-O(2) bond lengths are 1.92 Å. There is one shorter (2.15 Å) and one longer (2.39 Å) V(2)-O(4) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), two equivalent Na(2), one Mg(1), and one V(1) atom to form distorted ONa4MgV pentagonal pyramids that share corners with four equivalent O(1)Na4MgV pentagonal pyramids, corners with three equivalent O(4)Na2V3 trigonal bipyramids,  an edgeedge with one O(3)Na2MgV3 octahedra,  an edgeedge with one O(1)Na4MgV pentagonal pyramid, and  a faceface with one O(3)Na2MgV3 octahedra. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), one Mg(1), and one V(2) atom. In the third O site, O(3) is bonded to two equivalent Na(2), one Mg(1), one V(2), and two equivalent V(1) atoms to form distorted ONa2MgV3 octahedra that share corners with two equivalent O(3)Na2MgV3 octahedra, edges with two equivalent O(1)Na4MgV pentagonal pyramids, edges with two equivalent O(4)Na2V3 trigonal bipyramids, and faces with two equivalent O(1)Na4MgV pentagonal pyramids. The corner-sharing octahedral tilt angles are 2°. In the fourth O site, O(4) is bonded to two equivalent Na(1), one V(1), and two equivalent V(2) atoms to form ONa2V3 trigonal bipyramids that share corners with six equivalent O(1)Na4MgV pentagonal pyramids, corners with two equivalent O(4)Na2V3 trigonal bipyramids, and edges with two equivalent O(3)Na2MgV3 octahedra.