MgNb4Mn6O18 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(16), one O(17), one O(6), and one O(9) atom to form MgO4 tetrahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra, corners with two equivalent Mn(4)O4 tetrahedra, and  an edgeedge with one Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 20-58°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 5-coordinate geometry to one O(14), one O(18), one O(2), one O(7), and one O(8) atom. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(1), one O(13), one O(15), one O(3), one O(4), and one O(5) atom. In the third Nb site, Nb(3) is bonded to one O(10), one O(11), one O(12), one O(18), one O(6), and one O(7) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra and corners with three equivalent Mn(4)O4 tetrahedra. In the fourth Nb site, Nb(4) is bonded to one O(13), one O(16), one O(17), one O(3), one O(4), and one O(9) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mn(4)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. There are six inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 5-coordinate geometry to one O(10), one O(11), one O(12), one O(18), and one O(7) atom. In the second Mn site, Mn(2) is bonded to one O(1), one O(14), one O(15), one O(2), one O(5), and one O(8) atom to form distorted edge-sharing MnO6 octahedra. In the third Mn site, Mn(3) is bonded in a 6-coordinate geometry to one O(10), one O(12), one O(16), one O(17), one O(6), and one O(9) atom. In the fourth Mn site, Mn(4) is bonded to one O(10), one O(12), one O(6), and one O(9) atom to form distorted MnO4 tetrahedra that share  a cornercorner with one Nb(4)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 22-70°. In the fifth Mn site, Mn(5) is bonded to one O(1), one O(14), one O(15), one O(2), one O(5), and one O(8) atom to form edge-sharing MnO6 octahedra. In the sixth Mn site, Mn(6) is bonded in a 6-coordinate geometry to one O(1), one O(13), one O(15), one O(3), one O(4), and one O(5) atom. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal pyramidal geometry to one Nb(2), one Mn(2), one Mn(5), and one Mn(6) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Nb(1), one Mn(2), and one Mn(5) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(4), and one Mn(6) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Nb(2), one Nb(4), and one Mn(6) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Nb(2), one Mn(2), one Mn(5), and one Mn(6) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Nb(3), one Mn(3), and one Mn(4) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Nb(1), one Nb(3), and one Mn(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Nb(1), one Mn(2), and one Mn(5) atom. In the ninth O site, O(9) is bonded in a distorted see-saw-like geometry to one Mg(1), one Nb(4), one Mn(3), and one Mn(4) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Nb(3), one Mn(1), one Mn(3), and one Mn(4) atom. In the eleventh O site, O(11) is bonded in a water-like geometry to one Nb(3) and one Mn(1) atom. In the twelfth O site, O(12) is bonded in a tetrahedral geometry to one Nb(3), one Mn(1), one Mn(3), and one Mn(4) atom. In the thirteenth O site, O(13) is bonded in a T-shaped geometry to one Nb(2), one Nb(4), and one Mn(6) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Nb(1), one Mn(2), and one Mn(5) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Nb(2), one Mn(2), one Mn(5), and one Mn(6) atom. In the sixteenth O site, O(16) is bonded in a T-shaped geometry to one Mg(1), one Nb(4), and one Mn(3) atom. In the seventeenth O site, O(17) is bonded in a T-shaped geometry to one Mg(1), one Nb(4), and one Mn(3) atom. In the eighteenth O site, O(18) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(3), and one Mn(1) atom.
MgNb4Mn6O18 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(16), one O(17), one O(6), and one O(9) atom to form MgO4 tetrahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra, corners with two equivalent Mn(4)O4 tetrahedra, and  an edgeedge with one Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 20-58°. The Mg(1)-O(16) bond length is 1.96 Å. The Mg(1)-O(17) bond length is 1.90 Å. The Mg(1)-O(6) bond length is 1.98 Å. The Mg(1)-O(9) bond length is 1.96 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 5-coordinate geometry to one O(14), one O(18), one O(2), one O(7), and one O(8) atom. The Nb(1)-O(14) bond length is 1.89 Å. The Nb(1)-O(18) bond length is 2.48 Å. The Nb(1)-O(2) bond length is 1.87 Å. The Nb(1)-O(7) bond length is 2.01 Å. The Nb(1)-O(8) bond length is 1.88 Å. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(1), one O(13), one O(15), one O(3), one O(4), and one O(5) atom. The Nb(2)-O(1) bond length is 2.05 Å. The Nb(2)-O(13) bond length is 2.01 Å. The Nb(2)-O(15) bond length is 1.92 Å. The Nb(2)-O(3) bond length is 2.40 Å. The Nb(2)-O(4) bond length is 2.11 Å. The Nb(2)-O(5) bond length is 1.94 Å. In the third Nb site, Nb(3) is bonded to one O(10), one O(11), one O(12), one O(18), one O(6), and one O(7) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra and corners with three equivalent Mn(4)O4 tetrahedra. The Nb(3)-O(10) bond length is 2.03 Å. The Nb(3)-O(11) bond length is 1.95 Å. The Nb(3)-O(12) bond length is 2.20 Å. The Nb(3)-O(18) bond length is 1.92 Å. The Nb(3)-O(6) bond length is 2.06 Å. The Nb(3)-O(7) bond length is 2.04 Å. In the fourth Nb site, Nb(4) is bonded to one O(13), one O(16), one O(17), one O(3), one O(4), and one O(9) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mn(4)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The Nb(4)-O(13) bond length is 2.07 Å. The Nb(4)-O(16) bond length is 1.89 Å. The Nb(4)-O(17) bond length is 1.91 Å. The Nb(4)-O(3) bond length is 1.92 Å. The Nb(4)-O(4) bond length is 2.25 Å. The Nb(4)-O(9) bond length is 2.34 Å. There are six inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 5-coordinate geometry to one O(10), one O(11), one O(12), one O(18), and one O(7) atom. The Mn(1)-O(10) bond length is 2.00 Å. The Mn(1)-O(11) bond length is 1.89 Å. The Mn(1)-O(12) bond length is 2.04 Å. The Mn(1)-O(18) bond length is 2.00 Å. The Mn(1)-O(7) bond length is 2.11 Å. In the second Mn site, Mn(2) is bonded to one O(1), one O(14), one O(15), one O(2), one O(5), and one O(8) atom to form distorted edge-sharing MnO6 octahedra. The Mn(2)-O(1) bond length is 2.32 Å. The Mn(2)-O(14) bond length is 2.10 Å. The Mn(2)-O(15) bond length is 2.30 Å. The Mn(2)-O(2) bond length is 2.16 Å. The Mn(2)-O(5) bond length is 2.37 Å. The Mn(2)-O(8) bond length is 2.12 Å. In the third Mn site, Mn(3) is bonded in a 6-coordinate geometry to one O(10), one O(12), one O(16), one O(17), one O(6), and one O(9) atom. The Mn(3)-O(10) bond length is 2.57 Å. The Mn(3)-O(12) bond length is 2.14 Å. The Mn(3)-O(16) bond length is 2.09 Å. The Mn(3)-O(17) bond length is 2.06 Å. The Mn(3)-O(6) bond length is 2.48 Å. The Mn(3)-O(9) bond length is 2.11 Å. In the fourth Mn site, Mn(4) is bonded to one O(10), one O(12), one O(6), and one O(9) atom to form distorted MnO4 tetrahedra that share  a cornercorner with one Nb(4)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 22-70°. The Mn(4)-O(10) bond length is 2.13 Å. The Mn(4)-O(12) bond length is 2.02 Å. The Mn(4)-O(6) bond length is 2.07 Å. The Mn(4)-O(9) bond length is 2.18 Å. In the fifth Mn site, Mn(5) is bonded to one O(1), one O(14), one O(15), one O(2), one O(5), and one O(8) atom to form edge-sharing MnO6 octahedra. The Mn(5)-O(1) bond length is 2.26 Å. The Mn(5)-O(14) bond length is 2.21 Å. The Mn(5)-O(15) bond length is 2.26 Å. The Mn(5)-O(2) bond length is 2.22 Å. The Mn(5)-O(5) bond length is 2.35 Å. The Mn(5)-O(8) bond length is 2.23 Å. In the sixth Mn site, Mn(6) is bonded in a 6-coordinate geometry to one O(1), one O(13), one O(15), one O(3), one O(4), and one O(5) atom. The Mn(6)-O(1) bond length is 2.01 Å. The Mn(6)-O(13) bond length is 2.15 Å. The Mn(6)-O(15) bond length is 2.54 Å. The Mn(6)-O(3) bond length is 1.97 Å. The Mn(6)-O(4) bond length is 1.89 Å. The Mn(6)-O(5) bond length is 2.18 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal pyramidal geometry to one Nb(2), one Mn(2), one Mn(5), and one Mn(6) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Nb(1), one Mn(2), and one Mn(5) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(4), and one Mn(6) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Nb(2), one Nb(4), and one Mn(6) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Nb(2), one Mn(2), one Mn(5), and one Mn(6) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Nb(3), one Mn(3), and one Mn(4) atom. In the seventh O site, O(7) is bonded in a distorted T-shaped geometry to one Nb(1), one Nb(3), and one Mn(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Nb(1), one Mn(2), and one Mn(5) atom. In the ninth O site, O(9) is bonded in a distorted see-saw-like geometry to one Mg(1), one Nb(4), one Mn(3), and one Mn(4) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Nb(3), one Mn(1), one Mn(3), and one Mn(4) atom. In the eleventh O site, O(11) is bonded in a water-like geometry to one Nb(3) and one Mn(1) atom. In the twelfth O site, O(12) is bonded in a tetrahedral geometry to one Nb(3), one Mn(1), one Mn(3), and one Mn(4) atom. In the thirteenth O site, O(13) is bonded in a T-shaped geometry to one Nb(2), one Nb(4), and one Mn(6) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Nb(1), one Mn(2), and one Mn(5) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Nb(2), one Mn(2), one Mn(5), and one Mn(6) atom. In the sixteenth O site, O(16) is bonded in a T-shaped geometry to one Mg(1), one Nb(4), and one Mn(3) atom. In the seventeenth O site, O(17) is bonded in a T-shaped geometry to one Mg(1), one Nb(4), and one Mn(3) atom. In the eighteenth O site, O(18) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(3), and one Mn(1) atom.