Na2MgMn4O8 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(5), two equivalent O(2), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded to one O(1), one O(4), two equivalent O(3), and two equivalent O(8) atoms to form distorted NaO6 octahedra that share corners with four equivalent Mn(3)O5 square pyramids, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mn(3)O5 square pyramids. Mg(1) is bonded to one O(6), two equivalent O(4), and two equivalent O(7) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Mn(4)O6 octahedra, corners with two equivalent Mn(3)O5 square pyramids, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 13-83°. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 6-coordinate geometry to one O(3), one O(6), two equivalent O(1), and two equivalent O(5) atoms. In the second Mn site, Mn(2) is bonded to one O(5), one O(7), two equivalent O(2), and two equivalent O(6) atoms to form distorted MnO6 octahedra that share  a cornercorner with one Mn(3)O5 square pyramid, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. In the third Mn site, Mn(3) is bonded to one O(7), two equivalent O(3), and two equivalent O(8) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Mn(2)O6 octahedra, corners with four equivalent Na(2)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mn(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 11-27°. In the fourth Mn site, Mn(4) is bonded to one O(2), one O(8), two equivalent O(4), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with four equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, edges with two equivalent Mn(3)O5 square pyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), and two equivalent Mn(1) atoms to form distorted ONa2Mn2 tetrahedra that share  a cornercorner with one O(4)NaMg2Mn2 square pyramid, corners with two equivalent O(8)Na2Mn3 square pyramids, corners with two equivalent O(1)Na2Mn2 tetrahedra, corners with three equivalent O(5)NaMn3 trigonal pyramids, edges with two equivalent O(3)Na2Mn3 trigonal bipyramids, and  an edgeedge with one O(5)NaMn3 trigonal pyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to two equivalent Na(1), one Mn(4), and two equivalent Mn(2) atoms. In the third O site, O(3) is bonded to two equivalent Na(2), one Mn(1), and two equivalent Mn(3) atoms to form distorted ONa2Mn3 trigonal bipyramids that share corners with two equivalent O(7)Mg2Mn4 octahedra, corners with two equivalent O(4)NaMg2Mn2 square pyramids, corners with four equivalent O(8)Na2Mn3 square pyramids, corners with two equivalent O(5)NaMn3 trigonal pyramids, edges with two equivalent O(8)Na2Mn3 square pyramids, edges with two equivalent O(1)Na2Mn2 tetrahedra, and edges with two equivalent O(3)Na2Mn3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 77-83°. In the fourth O site, O(4) is bonded to one Na(2), two equivalent Mg(1), and two equivalent Mn(4) atoms to form distorted ONaMg2Mn2 square pyramids that share corners with four equivalent O(7)Mg2Mn4 octahedra,  a cornercorner with one O(1)Na2Mn2 tetrahedra, corners with two equivalent O(3)Na2Mn3 trigonal bipyramids, edges with two equivalent O(7)Mg2Mn4 octahedra, edges with two equivalent O(8)Na2Mn3 square pyramids, and edges with two equivalent O(4)NaMg2Mn2 square pyramids. The corner-sharing octahedral tilt angles range from 4-21°. In the fifth O site, O(5) is bonded to one Na(1), one Mn(2), and two equivalent Mn(1) atoms to form distorted ONaMn3 trigonal pyramids that share  a cornercorner with one O(7)Mg2Mn4 octahedra, corners with three equivalent O(1)Na2Mn2 tetrahedra, corners with two equivalent O(3)Na2Mn3 trigonal bipyramids, corners with two equivalent O(5)NaMn3 trigonal pyramids, and  an edgeedge with one O(1)Na2Mn2 tetrahedra. The corner-sharing octahedral tilt angles are 10°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to two equivalent Na(1), one Mg(1), one Mn(1), and two equivalent Mn(2) atoms. In the seventh O site, O(7) is bonded to two equivalent Mg(1), one Mn(2), one Mn(3), and two equivalent Mn(4) atoms to form distorted OMg2Mn4 octahedra that share corners with four equivalent O(4)NaMg2Mn2 square pyramids, corners with two equivalent O(3)Na2Mn3 trigonal bipyramids,  a cornercorner with one O(5)NaMn3 trigonal pyramid, edges with two equivalent O(7)Mg2Mn4 octahedra, edges with two equivalent O(8)Na2Mn3 square pyramids, and edges with two equivalent O(4)NaMg2Mn2 square pyramids. In the eighth O site, O(8) is bonded to two equivalent Na(2), one Mn(4), and two equivalent Mn(3) atoms to form distorted ONa2Mn3 square pyramids that share corners with two equivalent O(1)Na2Mn2 tetrahedra, corners with four equivalent O(3)Na2Mn3 trigonal bipyramids, edges with two equivalent O(7)Mg2Mn4 octahedra, edges with two equivalent O(8)Na2Mn3 square pyramids, edges with two equivalent O(4)NaMg2Mn2 square pyramids, and edges with two equivalent O(3)Na2Mn3 trigonal bipyramids.
Na2MgMn4O8 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(5), two equivalent O(2), and two equivalent O(6) atoms. The Na(1)-O(1) bond length is 2.27 Å. The Na(1)-O(5) bond length is 2.47 Å. There is one shorter (2.50 Å) and one longer (2.61 Å) Na(1)-O(2) bond length. There is one shorter (2.63 Å) and one longer (2.80 Å) Na(1)-O(6) bond length. In the second Na site, Na(2) is bonded to one O(1), one O(4), two equivalent O(3), and two equivalent O(8) atoms to form distorted NaO6 octahedra that share corners with four equivalent Mn(3)O5 square pyramids, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mn(3)O5 square pyramids. The Na(2)-O(1) bond length is 2.25 Å. The Na(2)-O(4) bond length is 2.52 Å. There is one shorter (2.30 Å) and one longer (2.46 Å) Na(2)-O(3) bond length. There is one shorter (2.27 Å) and one longer (2.42 Å) Na(2)-O(8) bond length. Mg(1) is bonded to one O(6), two equivalent O(4), and two equivalent O(7) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Mn(4)O6 octahedra, corners with two equivalent Mn(3)O5 square pyramids, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 13-83°. The Mg(1)-O(6) bond length is 2.06 Å. There is one shorter (2.03 Å) and one longer (2.08 Å) Mg(1)-O(4) bond length. There is one shorter (2.08 Å) and one longer (2.23 Å) Mg(1)-O(7) bond length. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 6-coordinate geometry to one O(3), one O(6), two equivalent O(1), and two equivalent O(5) atoms. The Mn(1)-O(3) bond length is 2.39 Å. The Mn(1)-O(6) bond length is 2.75 Å. There is one shorter (1.93 Å) and one longer (1.94 Å) Mn(1)-O(1) bond length. There is one shorter (1.97 Å) and one longer (1.98 Å) Mn(1)-O(5) bond length. In the second Mn site, Mn(2) is bonded to one O(5), one O(7), two equivalent O(2), and two equivalent O(6) atoms to form distorted MnO6 octahedra that share  a cornercorner with one Mn(3)O5 square pyramid, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The Mn(2)-O(5) bond length is 2.13 Å. The Mn(2)-O(7) bond length is 2.44 Å. There is one shorter (1.98 Å) and one longer (2.02 Å) Mn(2)-O(2) bond length. There is one shorter (1.96 Å) and one longer (1.99 Å) Mn(2)-O(6) bond length. In the third Mn site, Mn(3) is bonded to one O(7), two equivalent O(3), and two equivalent O(8) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Mn(2)O6 octahedra, corners with four equivalent Na(2)O6 octahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, and edges with two equivalent Mn(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 11-27°. The Mn(3)-O(7) bond length is 2.27 Å. There is one shorter (1.92 Å) and one longer (1.94 Å) Mn(3)-O(3) bond length. There is one shorter (1.96 Å) and one longer (2.00 Å) Mn(3)-O(8) bond length. In the fourth Mn site, Mn(4) is bonded to one O(2), one O(8), two equivalent O(4), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with four equivalent Mg(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, edges with two equivalent Mn(3)O5 square pyramids, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The Mn(4)-O(2) bond length is 1.97 Å. The Mn(4)-O(8) bond length is 2.01 Å. There is one shorter (1.97 Å) and one longer (2.28 Å) Mn(4)-O(4) bond length. There is one shorter (2.04 Å) and one longer (2.33 Å) Mn(4)-O(7) bond length. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), and two equivalent Mn(1) atoms to form distorted ONa2Mn2 tetrahedra that share  a cornercorner with one O(4)NaMg2Mn2 square pyramid, corners with two equivalent O(8)Na2Mn3 square pyramids, corners with two equivalent O(1)Na2Mn2 tetrahedra, corners with three equivalent O(5)NaMn3 trigonal pyramids, edges with two equivalent O(3)Na2Mn3 trigonal bipyramids, and  an edgeedge with one O(5)NaMn3 trigonal pyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to two equivalent Na(1), one Mn(4), and two equivalent Mn(2) atoms. In the third O site, O(3) is bonded to two equivalent Na(2), one Mn(1), and two equivalent Mn(3) atoms to form distorted ONa2Mn3 trigonal bipyramids that share corners with two equivalent O(7)Mg2Mn4 octahedra, corners with two equivalent O(4)NaMg2Mn2 square pyramids, corners with four equivalent O(8)Na2Mn3 square pyramids, corners with two equivalent O(5)NaMn3 trigonal pyramids, edges with two equivalent O(8)Na2Mn3 square pyramids, edges with two equivalent O(1)Na2Mn2 tetrahedra, and edges with two equivalent O(3)Na2Mn3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 77-83°. In the fourth O site, O(4) is bonded to one Na(2), two equivalent Mg(1), and two equivalent Mn(4) atoms to form distorted ONaMg2Mn2 square pyramids that share corners with four equivalent O(7)Mg2Mn4 octahedra,  a cornercorner with one O(1)Na2Mn2 tetrahedra, corners with two equivalent O(3)Na2Mn3 trigonal bipyramids, edges with two equivalent O(7)Mg2Mn4 octahedra, edges with two equivalent O(8)Na2Mn3 square pyramids, and edges with two equivalent O(4)NaMg2Mn2 square pyramids. The corner-sharing octahedral tilt angles range from 4-21°. In the fifth O site, O(5) is bonded to one Na(1), one Mn(2), and two equivalent Mn(1) atoms to form distorted ONaMn3 trigonal pyramids that share  a cornercorner with one O(7)Mg2Mn4 octahedra, corners with three equivalent O(1)Na2Mn2 tetrahedra, corners with two equivalent O(3)Na2Mn3 trigonal bipyramids, corners with two equivalent O(5)NaMn3 trigonal pyramids, and  an edgeedge with one O(1)Na2Mn2 tetrahedra. The corner-sharing octahedral tilt angles are 10°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to two equivalent Na(1), one Mg(1), one Mn(1), and two equivalent Mn(2) atoms. In the seventh O site, O(7) is bonded to two equivalent Mg(1), one Mn(2), one Mn(3), and two equivalent Mn(4) atoms to form distorted OMg2Mn4 octahedra that share corners with four equivalent O(4)NaMg2Mn2 square pyramids, corners with two equivalent O(3)Na2Mn3 trigonal bipyramids,  a cornercorner with one O(5)NaMn3 trigonal pyramid, edges with two equivalent O(7)Mg2Mn4 octahedra, edges with two equivalent O(8)Na2Mn3 square pyramids, and edges with two equivalent O(4)NaMg2Mn2 square pyramids. In the eighth O site, O(8) is bonded to two equivalent Na(2), one Mn(4), and two equivalent Mn(3) atoms to form distorted ONa2Mn3 square pyramids that share corners with two equivalent O(1)Na2Mn2 tetrahedra, corners with four equivalent O(3)Na2Mn3 trigonal bipyramids, edges with two equivalent O(7)Mg2Mn4 octahedra, edges with two equivalent O(8)Na2Mn3 square pyramids, edges with two equivalent O(4)NaMg2Mn2 square pyramids, and edges with two equivalent O(3)Na2Mn3 trigonal bipyramids.