Na2MgNb2O6 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with three equivalent Na(2)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, edges with three equivalent Nb(2)O6 octahedra,  a faceface with one Na(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-55°. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, corners with six equivalent Nb(1)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra,  a faceface with one Na(1)O6 octahedra, and  a faceface with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-62°. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form MgO6 octahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra, corners with six equivalent Nb(2)O6 octahedra, edges with three equivalent Na(2)O6 octahedra,  a faceface with one Na(1)O6 octahedra, and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-57°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NbO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with six equivalent Na(2)O6 octahedra, edges with three equivalent Na(1)O6 octahedra, edges with three equivalent Nb(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NbO6 octahedra that share corners with three equivalent Na(2)O6 octahedra, corners with six equivalent Mg(1)O6 octahedra, edges with three equivalent Na(1)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, and  a faceface with one Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-62°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids.
Na2MgNb2O6 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with three equivalent Na(2)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, edges with three equivalent Nb(2)O6 octahedra,  a faceface with one Na(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-55°. The Na(1)-O(1) bond length is 2.26 Å. The Na(1)-O(2) bond length is 2.35 Å. The Na(1)-O(3) bond length is 2.24 Å. The Na(1)-O(4) bond length is 2.24 Å. The Na(1)-O(5) bond length is 2.28 Å. The Na(1)-O(6) bond length is 2.21 Å. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, corners with six equivalent Nb(1)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra,  a faceface with one Na(1)O6 octahedra, and  a faceface with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-62°. The Na(2)-O(1) bond length is 2.43 Å. The Na(2)-O(2) bond length is 2.42 Å. The Na(2)-O(3) bond length is 2.48 Å. The Na(2)-O(4) bond length is 2.32 Å. The Na(2)-O(5) bond length is 2.32 Å. The Na(2)-O(6) bond length is 2.30 Å. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form MgO6 octahedra that share corners with three equivalent Na(1)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra, corners with six equivalent Nb(2)O6 octahedra, edges with three equivalent Na(2)O6 octahedra,  a faceface with one Na(1)O6 octahedra, and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-57°. The Mg(1)-O(1) bond length is 2.21 Å. The Mg(1)-O(2) bond length is 2.15 Å. The Mg(1)-O(3) bond length is 2.15 Å. The Mg(1)-O(4) bond length is 2.26 Å. The Mg(1)-O(5) bond length is 2.20 Å. The Mg(1)-O(6) bond length is 2.23 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NbO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with six equivalent Na(2)O6 octahedra, edges with three equivalent Na(1)O6 octahedra, edges with three equivalent Nb(2)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. The Nb(1)-O(1) bond length is 2.25 Å. The Nb(1)-O(2) bond length is 2.11 Å. The Nb(1)-O(3) bond length is 2.22 Å. The Nb(1)-O(4) bond length is 2.03 Å. The Nb(1)-O(5) bond length is 2.10 Å. The Nb(1)-O(6) bond length is 1.99 Å. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NbO6 octahedra that share corners with three equivalent Na(2)O6 octahedra, corners with six equivalent Mg(1)O6 octahedra, edges with three equivalent Na(1)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, and  a faceface with one Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-62°. The Nb(2)-O(1) bond length is 2.03 Å. The Nb(2)-O(2) bond length is 2.08 Å. The Nb(2)-O(3) bond length is 2.01 Å. The Nb(2)-O(4) bond length is 2.28 Å. The Nb(2)-O(5) bond length is 2.17 Å. The Nb(2)-O(6) bond length is 2.33 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Mg(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgNb2 trigonal bipyramids.