Mg14NbMnO16 is alpha Po-derived structured and crystallizes in the orthorhombic Pmmm space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(6), and two equivalent O(9) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, edges with four equivalent Mg(5)O6 octahedra, and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two O(2,2); two equivalent O(7); and two equivalent O(9) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra; corners with two equivalent Mg(2)O6 octahedra; corners with two equivalent Nb(1)O6 octahedra; edges with four equivalent Mg(4)O6 octahedra; edges with four Mg(6,6)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(4), one O(5), two equivalent O(3), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Mg(4)O6 octahedra; corners with four equivalent Mg(3)O6 octahedra; edges with two equivalent Mg(5)O6 octahedra; edges with two Mg(6,6)O6 octahedra; edges with two equivalent Nb(1)O6 octahedra; edges with two equivalent Mn(1)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the fourth Mg site, Mg(4) is bonded to one O(6), one O(7), two equivalent O(3), and two equivalent O(9) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fifth Mg site, Mg(5) is bonded to one O(4), one O(6), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(6)O6 octahedra, corners with four equivalent Mg(5)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the sixth Mg site, Mg(6) is bonded to one O(5), one O(7), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(5)O6 octahedra; corners with four Mg(6,6)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two equivalent Mg(3)O6 octahedra; edges with two equivalent Mg(4)O6 octahedra; edges with two equivalent Nb(1)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the seventh Mg site, Mg(6) is bonded to one O(5), one O(7), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(5)O6 octahedra; corners with four Mg(6,6)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two equivalent Mg(3)O6 octahedra; edges with two equivalent Mg(4)O6 octahedra; edges with two equivalent Nb(1)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the eighth Mg site, Mg(7) is bonded to one O(1), one O(2), one O(8), one O(9), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent Mg(7)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra,  an edgeedge with one Mn(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with two equivalent Mg(5)O6 octahedra, and edges with two equivalent Mg(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. Nb(1) is bonded to two O(2,2); two equivalent O(5); and two equivalent O(8) atoms to form NbO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with two equivalent Nb(1)O6 octahedra; corners with two equivalent Mn(1)O6 octahedra; edges with four equivalent Mg(3)O6 octahedra; edges with four Mg(6,6)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. Mn(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(8) atoms to form MnO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(3)O6 octahedra, edges with four equivalent Mg(5)O6 octahedra, and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Mg(5), two equivalent Mg(7), and one Mn(1) atom to form OMg5Mn octahedra that share corners with two equivalent O(2)Mg5Nb octahedra, corners with four equivalent O(1)Mg5Mn octahedra, edges with two equivalent O(4)Mg4Mn2 octahedra, edges with two equivalent O(8)Mg4MnNb octahedra, edges with two equivalent O(6)Mg6 octahedra, edges with two equivalent O(9)Mg6 octahedra, and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second O site, O(2) is bonded to one Mg(2), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom to form OMg5Nb octahedra that share corners with two equivalent O(1)Mg5Mn octahedra; corners with four O(2,2)Mg5Nb octahedra; edges with two equivalent O(8)Mg4MnNb octahedra; edges with two equivalent O(5)Mg4Nb2 octahedra; edges with two equivalent O(7)Mg6 octahedra; edges with two equivalent O(9)Mg6 octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the third O site, O(2) is bonded to one Mg(2), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom to form OMg5Nb octahedra that share corners with two equivalent O(1)Mg5Mn octahedra; corners with four O(2,2)Mg5Nb octahedra; edges with two equivalent O(8)Mg4MnNb octahedra; edges with two equivalent O(5)Mg4Nb2 octahedra; edges with two equivalent O(7)Mg6 octahedra; edges with two equivalent O(9)Mg6 octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the fourth O site, O(3) is bonded to one Mg(3), one Mg(4), one Mg(5), one Mg(6), and two equivalent Mg(7) atoms to form OMg6 octahedra that share corners with six equivalent O(3)Mg6 octahedra,  an edgeedge with one O(4)Mg4Mn2 octahedra,  an edgeedge with one O(5)Mg4Nb2 octahedra,  an edgeedge with one O(6)Mg6 octahedra,  an edgeedge with one O(7)Mg6 octahedra, edges with two equivalent O(8)Mg4MnNb octahedra, edges with two equivalent O(1)Mg5Mn octahedra, edges with two equivalent O(2)Mg5Nb octahedra, and edges with two equivalent O(9)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the fifth O site, O(4) is bonded to two equivalent Mg(3), two equivalent Mg(5), and two equivalent Mn(1) atoms to form OMg4Mn2 octahedra that share corners with two equivalent O(4)Mg4Mn2 octahedra, corners with two equivalent O(5)Mg4Nb2 octahedra, corners with two equivalent O(6)Mg6 octahedra, edges with four equivalent O(8)Mg4MnNb octahedra, edges with four equivalent O(1)Mg5Mn octahedra, and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the sixth O site, O(5) is bonded to two equivalent Mg(3); two Mg(6,6); and two equivalent Nb(1) atoms to form OMg4Nb2 octahedra that share corners with two equivalent O(4)Mg4Mn2 octahedra; corners with two equivalent O(5)Mg4Nb2 octahedra; corners with two equivalent O(7)Mg6 octahedra; edges with four equivalent O(8)Mg4MnNb octahedra; edges with four O(2,2)Mg5Nb octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the seventh O site, O(6) is bonded to two equivalent Mg(1), two equivalent Mg(4), and two equivalent Mg(5) atoms to form OMg6 octahedra that share corners with two equivalent O(4)Mg4Mn2 octahedra, corners with two equivalent O(6)Mg6 octahedra, corners with two equivalent O(7)Mg6 octahedra, edges with four equivalent O(1)Mg5Mn octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with four equivalent O(9)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the eighth O site, O(7) is bonded to two equivalent Mg(2); two equivalent Mg(4); and two Mg(6,6) atoms to form OMg6 octahedra that share corners with two equivalent O(5)Mg4Nb2 octahedra; corners with two equivalent O(6)Mg6 octahedra; corners with two equivalent O(7)Mg6 octahedra; edges with four O(2,2)Mg5Nb octahedra; edges with four equivalent O(3)Mg6 octahedra; and edges with four equivalent O(9)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the ninth O site, O(8) is bonded to two equivalent Mg(3), two equivalent Mg(7), one Nb(1), and one Mn(1) atom to form OMg4MnNb octahedra that share corners with two equivalent O(9)Mg6 octahedra; corners with four equivalent O(8)Mg4MnNb octahedra; edges with two equivalent O(4)Mg4Mn2 octahedra; edges with two equivalent O(5)Mg4Nb2 octahedra; edges with two equivalent O(1)Mg5Mn octahedra; edges with two O(2,2)Mg5Nb octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the tenth O site, O(9) is bonded to one Mg(1), one Mg(2), two equivalent Mg(4), and two equivalent Mg(7) atoms to form OMg6 octahedra that share corners with two equivalent O(8)Mg4MnNb octahedra; corners with four equivalent O(9)Mg6 octahedra; edges with two equivalent O(1)Mg5Mn octahedra; edges with two O(2,2)Mg5Nb octahedra; edges with two equivalent O(6)Mg6 octahedra; edges with two equivalent O(7)Mg6 octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
Mg14NbMnO16 is alpha Po-derived structured and crystallizes in the orthorhombic Pmmm space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(6), and two equivalent O(9) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, edges with four equivalent Mg(5)O6 octahedra, and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(1) bond lengths are 2.09 Å. Both Mg(1)-O(6) bond lengths are 2.16 Å. Both Mg(1)-O(9) bond lengths are 2.16 Å. In the second Mg site, Mg(2) is bonded to two O(2,2); two equivalent O(7); and two equivalent O(9) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra; corners with two equivalent Mg(2)O6 octahedra; corners with two equivalent Nb(1)O6 octahedra; edges with four equivalent Mg(4)O6 octahedra; edges with four Mg(6,6)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(2)-O(2,2) bond lengths are 2.05 Å. Both Mg(2)-O(7) bond lengths are 2.16 Å. Both Mg(2)-O(9) bond lengths are 2.16 Å. In the third Mg site, Mg(3) is bonded to one O(4), one O(5), two equivalent O(3), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Mg(4)O6 octahedra; corners with four equivalent Mg(3)O6 octahedra; edges with two equivalent Mg(5)O6 octahedra; edges with two Mg(6,6)O6 octahedra; edges with two equivalent Nb(1)O6 octahedra; edges with two equivalent Mn(1)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. The Mg(3)-O(4) bond length is 2.14 Å. The Mg(3)-O(5) bond length is 2.18 Å. Both Mg(3)-O(3) bond lengths are 2.14 Å. Both Mg(3)-O(8) bond lengths are 2.17 Å. In the fourth Mg site, Mg(4) is bonded to one O(6), one O(7), two equivalent O(3), and two equivalent O(9) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. The Mg(4)-O(6) bond length is 2.16 Å. The Mg(4)-O(7) bond length is 2.16 Å. Both Mg(4)-O(3) bond lengths are 2.17 Å. Both Mg(4)-O(9) bond lengths are 2.16 Å. In the fifth Mg site, Mg(5) is bonded to one O(4), one O(6), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(6)O6 octahedra, corners with four equivalent Mg(5)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. The Mg(5)-O(4) bond length is 2.17 Å. The Mg(5)-O(6) bond length is 2.14 Å. Both Mg(5)-O(1) bond lengths are 2.17 Å. Both Mg(5)-O(3) bond lengths are 2.16 Å. In the sixth Mg site, Mg(6) is bonded to one O(5), one O(7), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(5)O6 octahedra; corners with four Mg(6,6)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two equivalent Mg(3)O6 octahedra; edges with two equivalent Mg(4)O6 octahedra; edges with two equivalent Nb(1)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. The Mg(6)-O(5) bond length is 2.19 Å. The Mg(6)-O(7) bond length is 2.12 Å. Both Mg(6)-O(2) bond lengths are 2.17 Å. Both Mg(6)-O(3) bond lengths are 2.16 Å. In the seventh Mg site, Mg(6) is bonded to one O(5), one O(7), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(5)O6 octahedra; corners with four Mg(6,6)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two equivalent Mg(3)O6 octahedra; edges with two equivalent Mg(4)O6 octahedra; edges with two equivalent Nb(1)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. The Mg(6)-O(5) bond length is 2.19 Å. The Mg(6)-O(7) bond length is 2.12 Å. Both Mg(6)-O(2) bond lengths are 2.17 Å. Both Mg(6)-O(3) bond lengths are 2.16 Å. In the eighth Mg site, Mg(7) is bonded to one O(1), one O(2), one O(8), one O(9), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent Mg(7)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Nb(1)O6 octahedra,  an edgeedge with one Mn(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with two equivalent Mg(5)O6 octahedra, and edges with two equivalent Mg(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. The Mg(7)-O(1) bond length is 2.15 Å. The Mg(7)-O(2) bond length is 2.17 Å. The Mg(7)-O(8) bond length is 2.18 Å. The Mg(7)-O(9) bond length is 2.13 Å. Both Mg(7)-O(3) bond lengths are 2.17 Å. Nb(1) is bonded to two O(2,2); two equivalent O(5); and two equivalent O(8) atoms to form NbO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with two equivalent Nb(1)O6 octahedra; corners with two equivalent Mn(1)O6 octahedra; edges with four equivalent Mg(3)O6 octahedra; edges with four Mg(6,6)O6 octahedra; and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. Both Nb(1)-O(2,2) bond lengths are 2.26 Å. Both Nb(1)-O(5) bond lengths are 2.16 Å. Both Nb(1)-O(8) bond lengths are 2.21 Å. Mn(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(8) atoms to form MnO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, edges with four equivalent Mg(3)O6 octahedra, edges with four equivalent Mg(5)O6 octahedra, and edges with four equivalent Mg(7)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mn(1)-O(1) bond lengths are 2.22 Å. Both Mn(1)-O(4) bond lengths are 2.16 Å. Both Mn(1)-O(8) bond lengths are 2.11 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Mg(5), two equivalent Mg(7), and one Mn(1) atom to form OMg5Mn octahedra that share corners with two equivalent O(2)Mg5Nb octahedra, corners with four equivalent O(1)Mg5Mn octahedra, edges with two equivalent O(4)Mg4Mn2 octahedra, edges with two equivalent O(8)Mg4MnNb octahedra, edges with two equivalent O(6)Mg6 octahedra, edges with two equivalent O(9)Mg6 octahedra, and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second O site, O(2) is bonded to one Mg(2), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom to form OMg5Nb octahedra that share corners with two equivalent O(1)Mg5Mn octahedra; corners with four O(2,2)Mg5Nb octahedra; edges with two equivalent O(8)Mg4MnNb octahedra; edges with two equivalent O(5)Mg4Nb2 octahedra; edges with two equivalent O(7)Mg6 octahedra; edges with two equivalent O(9)Mg6 octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the third O site, O(2) is bonded to one Mg(2), two equivalent Mg(6), two equivalent Mg(7), and one Nb(1) atom to form OMg5Nb octahedra that share corners with two equivalent O(1)Mg5Mn octahedra; corners with four O(2,2)Mg5Nb octahedra; edges with two equivalent O(8)Mg4MnNb octahedra; edges with two equivalent O(5)Mg4Nb2 octahedra; edges with two equivalent O(7)Mg6 octahedra; edges with two equivalent O(9)Mg6 octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. Both O(2)-Mg(7) bond lengths are 2.17 Å. In the fourth O site, O(3) is bonded to one Mg(3), one Mg(4), one Mg(5), one Mg(6), and two equivalent Mg(7) atoms to form OMg6 octahedra that share corners with six equivalent O(3)Mg6 octahedra,  an edgeedge with one O(4)Mg4Mn2 octahedra,  an edgeedge with one O(5)Mg4Nb2 octahedra,  an edgeedge with one O(6)Mg6 octahedra,  an edgeedge with one O(7)Mg6 octahedra, edges with two equivalent O(8)Mg4MnNb octahedra, edges with two equivalent O(1)Mg5Mn octahedra, edges with two equivalent O(2)Mg5Nb octahedra, and edges with two equivalent O(9)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the fifth O site, O(4) is bonded to two equivalent Mg(3), two equivalent Mg(5), and two equivalent Mn(1) atoms to form OMg4Mn2 octahedra that share corners with two equivalent O(4)Mg4Mn2 octahedra, corners with two equivalent O(5)Mg4Nb2 octahedra, corners with two equivalent O(6)Mg6 octahedra, edges with four equivalent O(8)Mg4MnNb octahedra, edges with four equivalent O(1)Mg5Mn octahedra, and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the sixth O site, O(5) is bonded to two equivalent Mg(3); two Mg(6,6); and two equivalent Nb(1) atoms to form OMg4Nb2 octahedra that share corners with two equivalent O(4)Mg4Mn2 octahedra; corners with two equivalent O(5)Mg4Nb2 octahedra; corners with two equivalent O(7)Mg6 octahedra; edges with four equivalent O(8)Mg4MnNb octahedra; edges with four O(2,2)Mg5Nb octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the seventh O site, O(6) is bonded to two equivalent Mg(1), two equivalent Mg(4), and two equivalent Mg(5) atoms to form OMg6 octahedra that share corners with two equivalent O(4)Mg4Mn2 octahedra, corners with two equivalent O(6)Mg6 octahedra, corners with two equivalent O(7)Mg6 octahedra, edges with four equivalent O(1)Mg5Mn octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with four equivalent O(9)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the eighth O site, O(7) is bonded to two equivalent Mg(2); two equivalent Mg(4); and two Mg(6,6) atoms to form OMg6 octahedra that share corners with two equivalent O(5)Mg4Nb2 octahedra; corners with two equivalent O(6)Mg6 octahedra; corners with two equivalent O(7)Mg6 octahedra; edges with four O(2,2)Mg5Nb octahedra; edges with four equivalent O(3)Mg6 octahedra; and edges with four equivalent O(9)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the ninth O site, O(8) is bonded to two equivalent Mg(3), two equivalent Mg(7), one Nb(1), and one Mn(1) atom to form OMg4MnNb octahedra that share corners with two equivalent O(9)Mg6 octahedra; corners with four equivalent O(8)Mg4MnNb octahedra; edges with two equivalent O(4)Mg4Mn2 octahedra; edges with two equivalent O(5)Mg4Nb2 octahedra; edges with two equivalent O(1)Mg5Mn octahedra; edges with two O(2,2)Mg5Nb octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the tenth O site, O(9) is bonded to one Mg(1), one Mg(2), two equivalent Mg(4), and two equivalent Mg(7) atoms to form OMg6 octahedra that share corners with two equivalent O(8)Mg4MnNb octahedra; corners with four equivalent O(9)Mg6 octahedra; edges with two equivalent O(1)Mg5Mn octahedra; edges with two O(2,2)Mg5Nb octahedra; edges with two equivalent O(6)Mg6 octahedra; edges with two equivalent O(7)Mg6 octahedra; and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.