Na2MgNb2O6 crystallizes in the trigonal R-3 space group. Na(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and faces with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. Nb(1) is bonded to six equivalent O(1) atoms to form distorted NbO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. O(1) is bonded to two equivalent Na(1), one Mg(1), and two equivalent Nb(1) atoms to form a mixture of distorted corner and edge-sharing ONa2MgNb2 trigonal bipyramids.
Na2MgNb2O6 crystallizes in the trigonal R-3 space group. Na(1) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are three shorter (2.35 Å) and three longer (2.57 Å) Na(1)-O(1) bond lengths. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and faces with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. All Mg(1)-O(1) bond lengths are 2.11 Å. Nb(1) is bonded to six equivalent O(1) atoms to form distorted NbO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. There are three shorter (2.04 Å) and three longer (2.16 Å) Nb(1)-O(1) bond lengths. O(1) is bonded to two equivalent Na(1), one Mg(1), and two equivalent Nb(1) atoms to form a mixture of distorted corner and edge-sharing ONa2MgNb2 trigonal bipyramids.