Ba4MgTl8O16 crystallizes in the monoclinic Pm space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(16), one O(8), two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to one O(1), one O(9), two equivalent O(2), two equivalent O(5), and two equivalent O(6) atoms. In the third Ba site, Ba(3) is bonded in a 8-coordinate geometry to one O(16), one O(8), two equivalent O(11), two equivalent O(12), and two equivalent O(15) atoms. In the fourth Ba site, Ba(4) is bonded in a 8-coordinate geometry to one O(1), one O(9), two equivalent O(10), two equivalent O(13), and two equivalent O(14) atoms. Mg(1) is bonded to one O(10), one O(5), and two equivalent O(9) atoms to form MgO4 tetrahedra that share  a cornercorner with one Tl(1)O6 octahedra,  a cornercorner with one Tl(6)O6 octahedra, corners with two equivalent Tl(5)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Tl(3)O4 trigonal pyramids, and  an edgeedge with one Tl(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 17-36°. There are eight inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one O(14), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form TlO6 octahedra that share corners with two equivalent Tl(7)O6 octahedra,  a cornercorner with one Mg(1)O4 tetrahedra, edges with two equivalent Tl(1)O6 octahedra, edges with two equivalent Tl(8)O6 octahedra, and edges with two equivalent Tl(3)O4 trigonal pyramids. The corner-sharing octahedral tilt angles are 52°. In the second Tl site, Tl(2) is bonded to one O(16), one O(2), two equivalent O(15), and two equivalent O(4) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. In the third Tl site, Tl(3) is bonded to one O(3), one O(7), and two equivalent O(5) atoms to form TlO4 trigonal pyramids that share  a cornercorner with one Tl(8)O6 octahedra, corners with two equivalent Tl(6)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Tl(3)O4 trigonal pyramids, and edges with two equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-75°. In the fourth Tl site, Tl(4) is bonded to one O(11), one O(4), two equivalent O(6), and two equivalent O(8) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 52-57°. In the fifth Tl site, Tl(5) is bonded to one O(13), one O(6), two equivalent O(11), and two equivalent O(9) atoms to form distorted TlO6 octahedra that share corners with two equivalent Tl(7)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, edges with two equivalent Tl(4)O6 octahedra, edges with two equivalent Tl(5)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 66°. In the sixth Tl site, Tl(6) is bonded to one O(10), one O(8), two equivalent O(12), and two equivalent O(7) atoms to form distorted TlO6 octahedra that share corners with two equivalent Tl(4)O6 octahedra, corners with two equivalent Tl(8)O6 octahedra,  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Tl(3)O4 trigonal pyramids, and edges with two equivalent Tl(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-59°. In the seventh Tl site, Tl(7) is bonded to one O(1), one O(15), two equivalent O(13), and two equivalent O(2) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 52-66°. In the eighth Tl site, Tl(8) is bonded to one O(12), one O(3), two equivalent O(14), and two equivalent O(16) atoms to form TlO6 octahedra that share corners with two equivalent Tl(2)O6 octahedra, corners with two equivalent Tl(6)O6 octahedra,  a cornercorner with one Tl(3)O4 trigonal pyramid, edges with two equivalent Tl(1)O6 octahedra, and edges with two equivalent Tl(8)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-59°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded to one Ba(2), one Ba(4), one Tl(7), and two equivalent Tl(1) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(3)Ba2Tl4 octahedra,  a cornercorner with one O(15)Ba2Tl3 trigonal bipyramid, corners with two equivalent O(1)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids,  an edgeedge with one O(3)Ba2Tl4 octahedra, edges with two equivalent O(5)Ba2MgTl3 octahedra, edges with two equivalent O(14)Ba2Tl3 square pyramids, and edges with two equivalent O(2)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 6°. In the second O site, O(2) is bonded to two equivalent Ba(2), one Tl(2), and two equivalent Tl(7) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(5)Ba2MgTl3 octahedra,  a cornercorner with one O(16)Ba2Tl3 trigonal bipyramid, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids,  an edgeedge with one O(5)Ba2MgTl3 octahedra,  an edgeedge with one O(6)Ba2Tl3 trigonal bipyramid, edges with two equivalent O(1)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(15)Ba2Tl3 trigonal bipyramids, and edges with two equivalent O(2)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 42°. In the third O site, O(3) is bonded to two equivalent Ba(1), one Tl(3), one Tl(8), and two equivalent Tl(1) atoms to form OBa2Tl4 octahedra that share corners with two equivalent O(7)Ba2Tl3 square pyramids, corners with two equivalent O(1)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(5)Ba2MgTl3 octahedra, edges with two equivalent O(3)Ba2Tl4 octahedra, edges with two equivalent O(14)Ba2Tl3 square pyramids,  an edgeedge with one O(1)Ba2Tl3 trigonal bipyramid, edges with two equivalent O(16)Ba2Tl3 trigonal bipyramids, and  a faceface with one O(7)Ba2Tl3 square pyramid. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Ba(1), one Tl(4), and two equivalent Tl(2) atoms. In the fifth O site, O(5) is bonded to two equivalent Ba(2), one Mg(1), one Tl(1), and two equivalent Tl(3) atoms to form distorted OBa2MgTl3 octahedra that share  a cornercorner with one O(14)Ba2Tl3 square pyramid, corners with two equivalent O(7)Ba2Tl3 square pyramids, corners with two equivalent O(2)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(5)Ba2MgTl3 octahedra, edges with two equivalent O(3)Ba2Tl4 octahedra,  an edgeedge with one O(2)Ba2Tl3 trigonal bipyramid,  an edgeedge with one O(6)Ba2Tl3 trigonal bipyramid, and edges with two equivalent O(1)Ba2Tl3 trigonal bipyramids. In the sixth O site, O(6) is bonded to two equivalent Ba(2), one Tl(5), and two equivalent Tl(4) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(5)Ba2MgTl3 octahedra, corners with two equivalent O(1)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(2)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids,  an edgeedge with one O(5)Ba2MgTl3 octahedra, edges with two equivalent O(11)Ba2Tl3 square pyramids,  an edgeedge with one O(2)Ba2Tl3 trigonal bipyramid,  an edgeedge with one O(8)Ba2Tl3 trigonal bipyramid, and edges with two equivalent O(6)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. In the seventh O site, O(7) is bonded to two equivalent Ba(1), one Tl(3), and two equivalent Tl(6) atoms to form distorted OBa2Tl3 square pyramids that share corners with two equivalent O(5)Ba2MgTl3 octahedra, corners with two equivalent O(3)Ba2Tl4 octahedra, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(7)Ba2Tl3 square pyramids, edges with two equivalent O(8)Ba2Tl3 trigonal bipyramids, and  a faceface with one O(3)Ba2Tl4 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. In the eighth O site, O(8) is bonded to one Ba(1), one Ba(3), one Tl(6), and two equivalent Tl(4) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(3)Ba2Tl4 octahedra, corners with two equivalent O(15)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(11)Ba2Tl3 square pyramids, edges with two equivalent O(7)Ba2Tl3 square pyramids, and  an edgeedge with one O(6)Ba2Tl3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 47°. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Ba(2), one Ba(4), two equivalent Mg(1), and two equivalent Tl(5) atoms. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(4), one Mg(1), and one Tl(6) atom. In the eleventh O site, O(11) is bonded to two equivalent Ba(3), one Tl(4), and two equivalent Tl(5) atoms to form a mixture of edge and corner-sharing OBa2Tl3 square pyramids. In the twelfth O site, O(12) is bonded in a 5-coordinate geometry to two equivalent Ba(3), one Tl(8), and two equivalent Tl(6) atoms. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to two equivalent Ba(4), one Tl(5), and two equivalent Tl(7) atoms. In the fourteenth O site, O(14) is bonded to two equivalent Ba(4), one Tl(1), and two equivalent Tl(8) atoms to form distorted OBa2Tl3 square pyramids that share  a cornercorner with one O(5)Ba2MgTl3 octahedra, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(3)Ba2Tl4 octahedra, edges with two equivalent O(14)Ba2Tl3 square pyramids,  an edgeedge with one O(16)Ba2Tl3 trigonal bipyramid, and edges with two equivalent O(1)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. In the fifteenth O site, O(15) is bonded to two equivalent Ba(3), one Tl(7), and two equivalent Tl(2) atoms to form a mixture of distorted edge and corner-sharing OBa2Tl3 trigonal bipyramids. In the sixteenth O site, O(16) is bonded to one Ba(1), one Ba(3), one Tl(2), and two equivalent Tl(8) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(11)Ba2Tl3 square pyramids, corners with two equivalent O(14)Ba2Tl3 square pyramids, corners with two equivalent O(7)Ba2Tl3 square pyramids,  a cornercorner with one O(2)Ba2Tl3 trigonal bipyramid, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(3)Ba2Tl4 octahedra,  an edgeedge with one O(14)Ba2Tl3 square pyramid, and edges with two equivalent O(15)Ba2Tl3 trigonal bipyramids.
Ba4MgTl8O16 crystallizes in the monoclinic Pm space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(16), one O(8), two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms. The Ba(1)-O(16) bond length is 2.80 Å. The Ba(1)-O(8) bond length is 2.89 Å. Both Ba(1)-O(3) bond lengths are 2.96 Å. Both Ba(1)-O(4) bond lengths are 2.85 Å. Both Ba(1)-O(7) bond lengths are 2.76 Å. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to one O(1), one O(9), two equivalent O(2), two equivalent O(5), and two equivalent O(6) atoms. The Ba(2)-O(1) bond length is 3.11 Å. The Ba(2)-O(9) bond length is 3.05 Å. Both Ba(2)-O(2) bond lengths are 2.73 Å. Both Ba(2)-O(5) bond lengths are 2.79 Å. Both Ba(2)-O(6) bond lengths are 2.78 Å. In the third Ba site, Ba(3) is bonded in a 8-coordinate geometry to one O(16), one O(8), two equivalent O(11), two equivalent O(12), and two equivalent O(15) atoms. The Ba(3)-O(16) bond length is 2.88 Å. The Ba(3)-O(8) bond length is 2.91 Å. Both Ba(3)-O(11) bond lengths are 2.76 Å. Both Ba(3)-O(12) bond lengths are 2.88 Å. Both Ba(3)-O(15) bond lengths are 2.80 Å. In the fourth Ba site, Ba(4) is bonded in a 8-coordinate geometry to one O(1), one O(9), two equivalent O(10), two equivalent O(13), and two equivalent O(14) atoms. The Ba(4)-O(1) bond length is 2.97 Å. The Ba(4)-O(9) bond length is 2.91 Å. Both Ba(4)-O(10) bond lengths are 2.66 Å. Both Ba(4)-O(13) bond lengths are 3.06 Å. Both Ba(4)-O(14) bond lengths are 2.78 Å. Mg(1) is bonded to one O(10), one O(5), and two equivalent O(9) atoms to form MgO4 tetrahedra that share  a cornercorner with one Tl(1)O6 octahedra,  a cornercorner with one Tl(6)O6 octahedra, corners with two equivalent Tl(5)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Tl(3)O4 trigonal pyramids, and  an edgeedge with one Tl(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 17-36°. The Mg(1)-O(10) bond length is 1.96 Å. The Mg(1)-O(5) bond length is 2.02 Å. Both Mg(1)-O(9) bond lengths are 2.04 Å. There are eight inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one O(14), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form TlO6 octahedra that share corners with two equivalent Tl(7)O6 octahedra,  a cornercorner with one Mg(1)O4 tetrahedra, edges with two equivalent Tl(1)O6 octahedra, edges with two equivalent Tl(8)O6 octahedra, and edges with two equivalent Tl(3)O4 trigonal pyramids. The corner-sharing octahedral tilt angles are 52°. The Tl(1)-O(14) bond length is 2.29 Å. The Tl(1)-O(5) bond length is 2.63 Å. Both Tl(1)-O(1) bond lengths are 2.28 Å. Both Tl(1)-O(3) bond lengths are 2.48 Å. In the second Tl site, Tl(2) is bonded to one O(16), one O(2), two equivalent O(15), and two equivalent O(4) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. The Tl(2)-O(16) bond length is 2.42 Å. The Tl(2)-O(2) bond length is 2.25 Å. Both Tl(2)-O(15) bond lengths are 2.40 Å. Both Tl(2)-O(4) bond lengths are 2.43 Å. In the third Tl site, Tl(3) is bonded to one O(3), one O(7), and two equivalent O(5) atoms to form TlO4 trigonal pyramids that share  a cornercorner with one Tl(8)O6 octahedra, corners with two equivalent Tl(6)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Tl(3)O4 trigonal pyramids, and edges with two equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-75°. The Tl(3)-O(3) bond length is 2.41 Å. The Tl(3)-O(7) bond length is 2.28 Å. Both Tl(3)-O(5) bond lengths are 2.43 Å. In the fourth Tl site, Tl(4) is bonded to one O(11), one O(4), two equivalent O(6), and two equivalent O(8) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 52-57°. The Tl(4)-O(11) bond length is 2.36 Å. The Tl(4)-O(4) bond length is 2.37 Å. Both Tl(4)-O(6) bond lengths are 2.48 Å. Both Tl(4)-O(8) bond lengths are 2.29 Å. In the fifth Tl site, Tl(5) is bonded to one O(13), one O(6), two equivalent O(11), and two equivalent O(9) atoms to form distorted TlO6 octahedra that share corners with two equivalent Tl(7)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, edges with two equivalent Tl(4)O6 octahedra, edges with two equivalent Tl(5)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 66°. The Tl(5)-O(13) bond length is 2.22 Å. The Tl(5)-O(6) bond length is 2.23 Å. Both Tl(5)-O(11) bond lengths are 2.34 Å. Both Tl(5)-O(9) bond lengths are 2.64 Å. In the sixth Tl site, Tl(6) is bonded to one O(10), one O(8), two equivalent O(12), and two equivalent O(7) atoms to form distorted TlO6 octahedra that share corners with two equivalent Tl(4)O6 octahedra, corners with two equivalent Tl(8)O6 octahedra,  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Tl(3)O4 trigonal pyramids, and edges with two equivalent Tl(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-59°. The Tl(6)-O(10) bond length is 2.25 Å. The Tl(6)-O(8) bond length is 2.47 Å. Both Tl(6)-O(12) bond lengths are 2.41 Å. Both Tl(6)-O(7) bond lengths are 2.39 Å. In the seventh Tl site, Tl(7) is bonded to one O(1), one O(15), two equivalent O(13), and two equivalent O(2) atoms to form a mixture of edge and corner-sharing TlO6 octahedra. The corner-sharing octahedral tilt angles range from 52-66°. The Tl(7)-O(1) bond length is 2.36 Å. The Tl(7)-O(15) bond length is 2.29 Å. Both Tl(7)-O(13) bond lengths are 2.40 Å. Both Tl(7)-O(2) bond lengths are 2.44 Å. In the eighth Tl site, Tl(8) is bonded to one O(12), one O(3), two equivalent O(14), and two equivalent O(16) atoms to form TlO6 octahedra that share corners with two equivalent Tl(2)O6 octahedra, corners with two equivalent Tl(6)O6 octahedra,  a cornercorner with one Tl(3)O4 trigonal pyramid, edges with two equivalent Tl(1)O6 octahedra, and edges with two equivalent Tl(8)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-59°. The Tl(8)-O(12) bond length is 2.37 Å. The Tl(8)-O(3) bond length is 2.51 Å. Both Tl(8)-O(14) bond lengths are 2.40 Å. Both Tl(8)-O(16) bond lengths are 2.35 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded to one Ba(2), one Ba(4), one Tl(7), and two equivalent Tl(1) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(3)Ba2Tl4 octahedra,  a cornercorner with one O(15)Ba2Tl3 trigonal bipyramid, corners with two equivalent O(1)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids,  an edgeedge with one O(3)Ba2Tl4 octahedra, edges with two equivalent O(5)Ba2MgTl3 octahedra, edges with two equivalent O(14)Ba2Tl3 square pyramids, and edges with two equivalent O(2)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 6°. In the second O site, O(2) is bonded to two equivalent Ba(2), one Tl(2), and two equivalent Tl(7) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(5)Ba2MgTl3 octahedra,  a cornercorner with one O(16)Ba2Tl3 trigonal bipyramid, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids,  an edgeedge with one O(5)Ba2MgTl3 octahedra,  an edgeedge with one O(6)Ba2Tl3 trigonal bipyramid, edges with two equivalent O(1)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(15)Ba2Tl3 trigonal bipyramids, and edges with two equivalent O(2)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 42°. In the third O site, O(3) is bonded to two equivalent Ba(1), one Tl(3), one Tl(8), and two equivalent Tl(1) atoms to form OBa2Tl4 octahedra that share corners with two equivalent O(7)Ba2Tl3 square pyramids, corners with two equivalent O(1)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(5)Ba2MgTl3 octahedra, edges with two equivalent O(3)Ba2Tl4 octahedra, edges with two equivalent O(14)Ba2Tl3 square pyramids,  an edgeedge with one O(1)Ba2Tl3 trigonal bipyramid, edges with two equivalent O(16)Ba2Tl3 trigonal bipyramids, and  a faceface with one O(7)Ba2Tl3 square pyramid. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Ba(1), one Tl(4), and two equivalent Tl(2) atoms. In the fifth O site, O(5) is bonded to two equivalent Ba(2), one Mg(1), one Tl(1), and two equivalent Tl(3) atoms to form distorted OBa2MgTl3 octahedra that share  a cornercorner with one O(14)Ba2Tl3 square pyramid, corners with two equivalent O(7)Ba2Tl3 square pyramids, corners with two equivalent O(2)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(5)Ba2MgTl3 octahedra, edges with two equivalent O(3)Ba2Tl4 octahedra,  an edgeedge with one O(2)Ba2Tl3 trigonal bipyramid,  an edgeedge with one O(6)Ba2Tl3 trigonal bipyramid, and edges with two equivalent O(1)Ba2Tl3 trigonal bipyramids. In the sixth O site, O(6) is bonded to two equivalent Ba(2), one Tl(5), and two equivalent Tl(4) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(5)Ba2MgTl3 octahedra, corners with two equivalent O(1)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(2)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids,  an edgeedge with one O(5)Ba2MgTl3 octahedra, edges with two equivalent O(11)Ba2Tl3 square pyramids,  an edgeedge with one O(2)Ba2Tl3 trigonal bipyramid,  an edgeedge with one O(8)Ba2Tl3 trigonal bipyramid, and edges with two equivalent O(6)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. In the seventh O site, O(7) is bonded to two equivalent Ba(1), one Tl(3), and two equivalent Tl(6) atoms to form distorted OBa2Tl3 square pyramids that share corners with two equivalent O(5)Ba2MgTl3 octahedra, corners with two equivalent O(3)Ba2Tl4 octahedra, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(7)Ba2Tl3 square pyramids, edges with two equivalent O(8)Ba2Tl3 trigonal bipyramids, and  a faceface with one O(3)Ba2Tl4 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. In the eighth O site, O(8) is bonded to one Ba(1), one Ba(3), one Tl(6), and two equivalent Tl(4) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(3)Ba2Tl4 octahedra, corners with two equivalent O(15)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(6)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(11)Ba2Tl3 square pyramids, edges with two equivalent O(7)Ba2Tl3 square pyramids, and  an edgeedge with one O(6)Ba2Tl3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 47°. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Ba(2), one Ba(4), two equivalent Mg(1), and two equivalent Tl(5) atoms. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(4), one Mg(1), and one Tl(6) atom. In the eleventh O site, O(11) is bonded to two equivalent Ba(3), one Tl(4), and two equivalent Tl(5) atoms to form a mixture of edge and corner-sharing OBa2Tl3 square pyramids. In the twelfth O site, O(12) is bonded in a 5-coordinate geometry to two equivalent Ba(3), one Tl(8), and two equivalent Tl(6) atoms. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to two equivalent Ba(4), one Tl(5), and two equivalent Tl(7) atoms. In the fourteenth O site, O(14) is bonded to two equivalent Ba(4), one Tl(1), and two equivalent Tl(8) atoms to form distorted OBa2Tl3 square pyramids that share  a cornercorner with one O(5)Ba2MgTl3 octahedra, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(3)Ba2Tl4 octahedra, edges with two equivalent O(14)Ba2Tl3 square pyramids,  an edgeedge with one O(16)Ba2Tl3 trigonal bipyramid, and edges with two equivalent O(1)Ba2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. In the fifteenth O site, O(15) is bonded to two equivalent Ba(3), one Tl(7), and two equivalent Tl(2) atoms to form a mixture of distorted edge and corner-sharing OBa2Tl3 trigonal bipyramids. In the sixteenth O site, O(16) is bonded to one Ba(1), one Ba(3), one Tl(2), and two equivalent Tl(8) atoms to form distorted OBa2Tl3 trigonal bipyramids that share corners with two equivalent O(11)Ba2Tl3 square pyramids, corners with two equivalent O(14)Ba2Tl3 square pyramids, corners with two equivalent O(7)Ba2Tl3 square pyramids,  a cornercorner with one O(2)Ba2Tl3 trigonal bipyramid, corners with two equivalent O(16)Ba2Tl3 trigonal bipyramids, corners with two equivalent O(8)Ba2Tl3 trigonal bipyramids, edges with two equivalent O(3)Ba2Tl4 octahedra,  an edgeedge with one O(14)Ba2Tl3 square pyramid, and edges with two equivalent O(15)Ba2Tl3 trigonal bipyramids.