Na4Mg(BiO3)2 crystallizes in the monoclinic Cm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a distorted see-saw-like geometry to one O(1), one O(4), and two equivalent O(2) atoms. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. Mg(1) is bonded to one O(1), one O(4), and two equivalent O(3) atoms to form MgO4 tetrahedra that share corners with eight equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-59°. Bi(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form BiO6 octahedra that share corners with four equivalent Mg(1)O4 tetrahedra and edges with three equivalent Bi(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(2), two equivalent Na(1), one Mg(1), and two equivalent Bi(1) atoms. In the second O site, O(2) is bonded to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Bi(1) atoms to form edge-sharing ONa4Bi2 octahedra. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Mg(1), and two equivalent Bi(1) atoms. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), and two equivalent Bi(1) atoms.
Na4Mg(BiO3)2 crystallizes in the monoclinic Cm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. The Na(1)-O(1) bond length is 2.52 Å. The Na(1)-O(3) bond length is 2.30 Å. There is one shorter (2.36 Å) and one longer (2.38 Å) Na(1)-O(2) bond length. In the second Na site, Na(2) is bonded in a distorted see-saw-like geometry to one O(1), one O(4), and two equivalent O(2) atoms. The Na(2)-O(1) bond length is 2.27 Å. The Na(2)-O(4) bond length is 2.38 Å. Both Na(2)-O(2) bond lengths are 2.40 Å. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. The Na(3)-O(4) bond length is 2.39 Å. Both Na(3)-O(2) bond lengths are 2.48 Å. Both Na(3)-O(3) bond lengths are 2.50 Å. Mg(1) is bonded to one O(1), one O(4), and two equivalent O(3) atoms to form MgO4 tetrahedra that share corners with eight equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-59°. The Mg(1)-O(1) bond length is 1.97 Å. The Mg(1)-O(4) bond length is 2.01 Å. Both Mg(1)-O(3) bond lengths are 2.01 Å. Bi(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form BiO6 octahedra that share corners with four equivalent Mg(1)O4 tetrahedra and edges with three equivalent Bi(1)O6 octahedra. The Bi(1)-O(1) bond length is 2.66 Å. The Bi(1)-O(4) bond length is 2.54 Å. There is one shorter (2.31 Å) and one longer (2.32 Å) Bi(1)-O(2) bond length. There is one shorter (2.34 Å) and one longer (2.63 Å) Bi(1)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(2), two equivalent Na(1), one Mg(1), and two equivalent Bi(1) atoms. In the second O site, O(2) is bonded to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Bi(1) atoms to form edge-sharing ONa4Bi2 octahedra. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Mg(1), and two equivalent Bi(1) atoms. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), and two equivalent Bi(1) atoms.