Ba6MgCo2(Sb2O9)2 crystallizes in the triclinic P1 space group. There are six inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(12), one O(14), one O(15), one O(16), one O(8), one O(9), two equivalent O(4), two equivalent O(6), and two equivalent O(7) atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Sb(3)O6 octahedra,  a faceface with one Ba(4)O12 cuboctahedra, faces with three equivalent Ba(3)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra,  a faceface with one Sb(4)O6 octahedra, faces with three equivalent Co(2)O6 octahedra, and faces with three equivalent Sb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-14°. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(5), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the third Ba site, Ba(3) is bonded to one O(13), one O(17), one O(18), one O(4), one O(6), one O(7), two equivalent O(12), two equivalent O(8), and two equivalent O(9) atoms to form distorted BaO12 cuboctahedra that share corners with three equivalent Ba(5)O12 cuboctahedra, corners with six equivalent Ba(3)O12 cuboctahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, faces with three equivalent Ba(1)O12 cuboctahedra,  a faceface with one Sb(2)O6 octahedra, faces with three equivalent Co(2)O6 octahedra, and faces with three equivalent Sb(4)O6 octahedra. In the fourth Ba site, Ba(4) is bonded to one O(1), one O(14), one O(15), one O(16), one O(2), one O(3), two equivalent O(10), two equivalent O(11), and two equivalent O(5) atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent Ba(4)O12 cuboctahedra, corners with three equivalent Sb(2)O6 octahedra, corners with three equivalent Mg(1)O5 trigonal bipyramids,  a faceface with one Ba(1)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra, faces with three equivalent Co(1)O6 octahedra, and faces with three equivalent Sb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-9°. In the fifth Ba site, Ba(5) is bonded to one O(10), one O(11), one O(4), one O(5), one O(6), one O(7), two equivalent O(14), two equivalent O(15), and two equivalent O(16) atoms to form distorted BaO12 cuboctahedra that share corners with three equivalent Ba(3)O12 cuboctahedra, corners with six equivalent Ba(5)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Ba(4)O12 cuboctahedra,  a faceface with one Co(1)O6 octahedra,  a faceface with one Co(2)O6 octahedra, faces with three equivalent Sb(2)O6 octahedra, and faces with three equivalent Sb(3)O6 octahedra. In the sixth Ba site, Ba(6) is bonded in a 9-coordinate geometry to one O(12), one O(8), one O(9), two equivalent O(13), two equivalent O(17), and two equivalent O(18) atoms. Mg(1) is bonded to one O(1), one O(13), one O(17), one O(2), and one O(3) atom to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Ba(3)O12 cuboctahedra, corners with three equivalent Ba(4)O12 cuboctahedra,  an edgeedge with one Sb(4)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(10), one O(11), one O(2), one O(3), and one O(5) atom to form distorted CoO6 octahedra that share corners with three equivalent Sb(3)O6 octahedra,  a faceface with one Ba(5)O12 cuboctahedra, faces with three equivalent Ba(4)O12 cuboctahedra, and  a faceface with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 5-10°. In the second Co site, Co(2) is bonded to one O(12), one O(4), one O(6), one O(7), one O(8), and one O(9) atom to form CoO6 octahedra that share corners with three equivalent Sb(2)O6 octahedra, corners with three equivalent Sb(4)O6 octahedra,  a faceface with one Ba(5)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with three equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-11°. There are four inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(18), one O(2), and one O(3) atom. In the second Sb site, Sb(2) is bonded to one O(14), one O(15), one O(16), one O(4), one O(6), and one O(7) atom to form SbO6 octahedra that share corners with three equivalent Ba(4)O12 cuboctahedra, corners with three equivalent Co(2)O6 octahedra,  a faceface with one Ba(3)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra, and  a faceface with one Sb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-11°. In the third Sb site, Sb(3) is bonded to one O(10), one O(11), one O(14), one O(15), one O(16), and one O(5) atom to form SbO6 octahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Co(1)O6 octahedra, faces with three equivalent Ba(4)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra, and  a faceface with one Sb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-10°. In the fourth Sb site, Sb(4) is bonded to one O(12), one O(13), one O(17), one O(18), one O(8), and one O(9) atom to form SbO6 octahedra that share corners with three equivalent Co(2)O6 octahedra,  an edgeedge with one Mg(1)O5 trigonal bipyramid,  a faceface with one Ba(1)O12 cuboctahedra, and faces with three equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-9°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(4), two equivalent Ba(2), one Mg(1), one Co(1), and one Sb(1) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Ba(4), two equivalent Ba(2), one Mg(1), one Co(1), and one Sb(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(4), two equivalent Ba(2), one Mg(1), one Co(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Ba(3), one Ba(5), two equivalent Ba(1), one Co(2), and one Sb(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(4), one Co(1), and one Sb(3) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ba(3), one Ba(5), two equivalent Ba(1), one Co(2), and one Sb(2) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Ba(3), one Ba(5), two equivalent Ba(1), one Co(2), and one Sb(2) atom. In the eighth O site, O(8) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(6), two equivalent Ba(3), one Co(2), and one Sb(4) atom. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(6), two equivalent Ba(3), one Co(2), and one Sb(4) atom. In the tenth O site, O(10) is bonded to one Ba(2), one Ba(5), two equivalent Ba(4), one Co(1), and one Sb(3) atom to form distorted corner-sharing OBa4CoSb octahedra. The corner-sharing octahedral tilt angles are 2°. In the eleventh O site, O(11) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(4), one Co(1), and one Sb(3) atom. In the twelfth O site, O(12) is bonded to one Ba(1), one Ba(6), two equivalent Ba(3), one Co(2), and one Sb(4) atom to form distorted corner-sharing OBa4CoSb octahedra. The corner-sharing octahedral tilt angles are 6°. In the thirteenth O site, O(13) is bonded in a distorted L-shaped geometry to one Ba(3), two equivalent Ba(6), one Mg(1), and one Sb(4) atom. In the fourteenth O site, O(14) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Sb(2), and one Sb(3) atom. In the fifteenth O site, O(15) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Sb(2), and one Sb(3) atom. In the sixteenth O site, O(16) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Sb(2), and one Sb(3) atom. In the seventeenth O site, O(17) is bonded in a 2-coordinate geometry to one Ba(3), two equivalent Ba(6), one Mg(1), and one Sb(4) atom. In the eighteenth O site, O(18) is bonded in a 4-coordinate geometry to one Ba(3), two equivalent Ba(6), one Sb(1), and one Sb(4) atom.
Ba6MgCo2(Sb2O9)2 crystallizes in the triclinic P1 space group. There are six inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(12), one O(14), one O(15), one O(16), one O(8), one O(9), two equivalent O(4), two equivalent O(6), and two equivalent O(7) atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Sb(3)O6 octahedra,  a faceface with one Ba(4)O12 cuboctahedra, faces with three equivalent Ba(3)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra,  a faceface with one Sb(4)O6 octahedra, faces with three equivalent Co(2)O6 octahedra, and faces with three equivalent Sb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-14°. The Ba(1)-O(12) bond length is 2.84 Å. The Ba(1)-O(14) bond length is 3.31 Å. The Ba(1)-O(15) bond length is 3.28 Å. The Ba(1)-O(16) bond length is 3.18 Å. The Ba(1)-O(8) bond length is 2.82 Å. The Ba(1)-O(9) bond length is 2.89 Å. There is one shorter (2.87 Å) and one longer (3.08 Å) Ba(1)-O(4) bond length. There is one shorter (2.89 Å) and one longer (3.08 Å) Ba(1)-O(6) bond length. There is one shorter (2.91 Å) and one longer (3.05 Å) Ba(1)-O(7) bond length. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(5), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Ba(2)-O(10) bond length is 2.77 Å. The Ba(2)-O(11) bond length is 2.84 Å. The Ba(2)-O(5) bond length is 2.73 Å. There is one shorter (2.81 Å) and one longer (3.22 Å) Ba(2)-O(1) bond length. There is one shorter (2.83 Å) and one longer (3.13 Å) Ba(2)-O(2) bond length. There is one shorter (2.91 Å) and one longer (3.11 Å) Ba(2)-O(3) bond length. In the third Ba site, Ba(3) is bonded to one O(13), one O(17), one O(18), one O(4), one O(6), one O(7), two equivalent O(12), two equivalent O(8), and two equivalent O(9) atoms to form distorted BaO12 cuboctahedra that share corners with three equivalent Ba(5)O12 cuboctahedra, corners with six equivalent Ba(3)O12 cuboctahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, faces with three equivalent Ba(1)O12 cuboctahedra,  a faceface with one Sb(2)O6 octahedra, faces with three equivalent Co(2)O6 octahedra, and faces with three equivalent Sb(4)O6 octahedra. The Ba(3)-O(13) bond length is 3.05 Å. The Ba(3)-O(17) bond length is 3.05 Å. The Ba(3)-O(18) bond length is 2.74 Å. The Ba(3)-O(4) bond length is 3.16 Å. The Ba(3)-O(6) bond length is 3.10 Å. The Ba(3)-O(7) bond length is 3.17 Å. There is one shorter (2.90 Å) and one longer (3.05 Å) Ba(3)-O(12) bond length. There is one shorter (2.81 Å) and one longer (3.16 Å) Ba(3)-O(8) bond length. There is one shorter (2.85 Å) and one longer (3.09 Å) Ba(3)-O(9) bond length. In the fourth Ba site, Ba(4) is bonded to one O(1), one O(14), one O(15), one O(16), one O(2), one O(3), two equivalent O(10), two equivalent O(11), and two equivalent O(5) atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent Ba(4)O12 cuboctahedra, corners with three equivalent Sb(2)O6 octahedra, corners with three equivalent Mg(1)O5 trigonal bipyramids,  a faceface with one Ba(1)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra, faces with three equivalent Co(1)O6 octahedra, and faces with three equivalent Sb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-9°. The Ba(4)-O(1) bond length is 3.30 Å. The Ba(4)-O(14) bond length is 3.00 Å. The Ba(4)-O(15) bond length is 3.04 Å. The Ba(4)-O(16) bond length is 3.16 Å. The Ba(4)-O(2) bond length is 3.18 Å. The Ba(4)-O(3) bond length is 3.21 Å. There is one shorter (2.87 Å) and one longer (3.06 Å) Ba(4)-O(10) bond length. There is one shorter (2.82 Å) and one longer (3.14 Å) Ba(4)-O(11) bond length. There is one shorter (2.84 Å) and one longer (3.11 Å) Ba(4)-O(5) bond length. In the fifth Ba site, Ba(5) is bonded to one O(10), one O(11), one O(4), one O(5), one O(6), one O(7), two equivalent O(14), two equivalent O(15), and two equivalent O(16) atoms to form distorted BaO12 cuboctahedra that share corners with three equivalent Ba(3)O12 cuboctahedra, corners with six equivalent Ba(5)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Ba(4)O12 cuboctahedra,  a faceface with one Co(1)O6 octahedra,  a faceface with one Co(2)O6 octahedra, faces with three equivalent Sb(2)O6 octahedra, and faces with three equivalent Sb(3)O6 octahedra. The Ba(5)-O(10) bond length is 3.11 Å. The Ba(5)-O(11) bond length is 3.08 Å. The Ba(5)-O(4) bond length is 2.86 Å. The Ba(5)-O(5) bond length is 3.30 Å. The Ba(5)-O(6) bond length is 2.93 Å. The Ba(5)-O(7) bond length is 2.83 Å. There is one shorter (2.92 Å) and one longer (3.07 Å) Ba(5)-O(14) bond length. There is one shorter (2.89 Å) and one longer (3.07 Å) Ba(5)-O(15) bond length. There is one shorter (2.91 Å) and one longer (3.04 Å) Ba(5)-O(16) bond length. In the sixth Ba site, Ba(6) is bonded in a 9-coordinate geometry to one O(12), one O(8), one O(9), two equivalent O(13), two equivalent O(17), and two equivalent O(18) atoms. The Ba(6)-O(12) bond length is 2.71 Å. The Ba(6)-O(8) bond length is 2.72 Å. The Ba(6)-O(9) bond length is 2.69 Å. There is one shorter (2.92 Å) and one longer (3.11 Å) Ba(6)-O(13) bond length. There is one shorter (2.76 Å) and one longer (3.29 Å) Ba(6)-O(17) bond length. There is one shorter (2.77 Å) and one longer (3.18 Å) Ba(6)-O(18) bond length. Mg(1) is bonded to one O(1), one O(13), one O(17), one O(2), and one O(3) atom to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Ba(3)O12 cuboctahedra, corners with three equivalent Ba(4)O12 cuboctahedra,  an edgeedge with one Sb(4)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The Mg(1)-O(1) bond length is 2.12 Å. The Mg(1)-O(13) bond length is 2.09 Å. The Mg(1)-O(17) bond length is 2.09 Å. The Mg(1)-O(2) bond length is 2.20 Å. The Mg(1)-O(3) bond length is 2.06 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(10), one O(11), one O(2), one O(3), and one O(5) atom to form distorted CoO6 octahedra that share corners with three equivalent Sb(3)O6 octahedra,  a faceface with one Ba(5)O12 cuboctahedra, faces with three equivalent Ba(4)O12 cuboctahedra, and  a faceface with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 5-10°. The Co(1)-O(1) bond length is 2.20 Å. The Co(1)-O(10) bond length is 2.11 Å. The Co(1)-O(11) bond length is 2.11 Å. The Co(1)-O(2) bond length is 2.07 Å. The Co(1)-O(3) bond length is 2.48 Å. The Co(1)-O(5) bond length is 2.12 Å. In the second Co site, Co(2) is bonded to one O(12), one O(4), one O(6), one O(7), one O(8), and one O(9) atom to form CoO6 octahedra that share corners with three equivalent Sb(2)O6 octahedra, corners with three equivalent Sb(4)O6 octahedra,  a faceface with one Ba(5)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with three equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-11°. The Co(2)-O(12) bond length is 2.14 Å. The Co(2)-O(4) bond length is 2.15 Å. The Co(2)-O(6) bond length is 2.14 Å. The Co(2)-O(7) bond length is 2.18 Å. The Co(2)-O(8) bond length is 2.14 Å. The Co(2)-O(9) bond length is 2.19 Å. There are four inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(18), one O(2), and one O(3) atom. The Sb(1)-O(1) bond length is 2.09 Å. The Sb(1)-O(18) bond length is 2.36 Å. The Sb(1)-O(2) bond length is 2.15 Å. The Sb(1)-O(3) bond length is 2.07 Å. In the second Sb site, Sb(2) is bonded to one O(14), one O(15), one O(16), one O(4), one O(6), and one O(7) atom to form SbO6 octahedra that share corners with three equivalent Ba(4)O12 cuboctahedra, corners with three equivalent Co(2)O6 octahedra,  a faceface with one Ba(3)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra, and  a faceface with one Sb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-11°. The Sb(2)-O(14) bond length is 2.13 Å. The Sb(2)-O(15) bond length is 2.14 Å. The Sb(2)-O(16) bond length is 2.11 Å. The Sb(2)-O(4) bond length is 1.95 Å. The Sb(2)-O(6) bond length is 1.95 Å. The Sb(2)-O(7) bond length is 1.96 Å. In the third Sb site, Sb(3) is bonded to one O(10), one O(11), one O(14), one O(15), one O(16), and one O(5) atom to form SbO6 octahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Co(1)O6 octahedra, faces with three equivalent Ba(4)O12 cuboctahedra, faces with three equivalent Ba(5)O12 cuboctahedra, and  a faceface with one Sb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-10°. The Sb(3)-O(10) bond length is 1.98 Å. The Sb(3)-O(11) bond length is 1.99 Å. The Sb(3)-O(14) bond length is 2.06 Å. The Sb(3)-O(15) bond length is 2.06 Å. The Sb(3)-O(16) bond length is 2.06 Å. The Sb(3)-O(5) bond length is 1.99 Å. In the fourth Sb site, Sb(4) is bonded to one O(12), one O(13), one O(17), one O(18), one O(8), and one O(9) atom to form SbO6 octahedra that share corners with three equivalent Co(2)O6 octahedra,  an edgeedge with one Mg(1)O5 trigonal bipyramid,  a faceface with one Ba(1)O12 cuboctahedra, and faces with three equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-9°. The Sb(4)-O(12) bond length is 2.04 Å. The Sb(4)-O(13) bond length is 2.02 Å. The Sb(4)-O(17) bond length is 2.03 Å. The Sb(4)-O(18) bond length is 2.02 Å. The Sb(4)-O(8) bond length is 2.05 Å. The Sb(4)-O(9) bond length is 2.04 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(4), two equivalent Ba(2), one Mg(1), one Co(1), and one Sb(1) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Ba(4), two equivalent Ba(2), one Mg(1), one Co(1), and one Sb(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(4), two equivalent Ba(2), one Mg(1), one Co(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Ba(3), one Ba(5), two equivalent Ba(1), one Co(2), and one Sb(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(4), one Co(1), and one Sb(3) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ba(3), one Ba(5), two equivalent Ba(1), one Co(2), and one Sb(2) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Ba(3), one Ba(5), two equivalent Ba(1), one Co(2), and one Sb(2) atom. In the eighth O site, O(8) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(6), two equivalent Ba(3), one Co(2), and one Sb(4) atom. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(6), two equivalent Ba(3), one Co(2), and one Sb(4) atom. In the tenth O site, O(10) is bonded to one Ba(2), one Ba(5), two equivalent Ba(4), one Co(1), and one Sb(3) atom to form distorted corner-sharing OBa4CoSb octahedra. The corner-sharing octahedral tilt angles are 2°. In the eleventh O site, O(11) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(5), two equivalent Ba(4), one Co(1), and one Sb(3) atom. In the twelfth O site, O(12) is bonded to one Ba(1), one Ba(6), two equivalent Ba(3), one Co(2), and one Sb(4) atom to form distorted corner-sharing OBa4CoSb octahedra. The corner-sharing octahedral tilt angles are 6°. In the thirteenth O site, O(13) is bonded in a distorted L-shaped geometry to one Ba(3), two equivalent Ba(6), one Mg(1), and one Sb(4) atom. In the fourteenth O site, O(14) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Sb(2), and one Sb(3) atom. In the fifteenth O site, O(15) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Sb(2), and one Sb(3) atom. In the sixteenth O site, O(16) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(5), one Sb(2), and one Sb(3) atom. In the seventeenth O site, O(17) is bonded in a 2-coordinate geometry to one Ba(3), two equivalent Ba(6), one Mg(1), and one Sb(4) atom. In the eighteenth O site, O(18) is bonded in a 4-coordinate geometry to one Ba(3), two equivalent Ba(6), one Sb(1), and one Sb(4) atom.