Ba3MgNb2CoO9 crystallizes in the triclinic P1 space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(1), one O(3), one O(4), one O(6), one O(7), one O(9), two equivalent O(2), two equivalent O(5), and two equivalent O(8) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Nb(2)O6 octahedra, faces with three equivalent Nb(1)O6 octahedra, and faces with three equivalent Co(1)O6 octahedra. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one Mg(1), one O(1), one O(2), one O(5), one O(6), one O(8), one O(9), and two equivalent O(4) atoms. In the third Ba site, Ba(3) is bonded in a 9-coordinate geometry to one Mg(1), one O(2), one O(3), one O(4), one O(5), one O(7), one O(8), and two equivalent O(6) atoms. Mg(1) is bonded in a rectangular see-saw-like geometry to one Ba(2), one Ba(3), one O(1), one O(3), one O(7), and one O(9) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(8), and one O(9) atom to form NbO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Co(1)O6 octahedra, and faces with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. In the second Nb site, Nb(2) is bonded to one O(1), one O(3), one O(4), one O(6), one O(7), and one O(9) atom to form NbO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Co(1)O6 octahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. Co(1) is bonded to one O(2), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, and faces with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-6°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ba(1), one Ba(2), one Mg(1), one Nb(1), and one Nb(2) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Nb(1), and one Co(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(3), one Mg(1), one Nb(2), and one Co(1) atom. In the fourth O site, O(4) is bonded to one Ba(1), one Ba(3), two equivalent Ba(2), one Nb(1), and one Nb(2) atom to form distorted corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles are 22°. In the fifth O site, O(5) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Nb(1), and one Co(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), two equivalent Ba(3), one Nb(2), and one Co(1) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(3), one Mg(1), one Nb(2), and one Co(1) atom. In the eighth O site, O(8) is bonded in a 1-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Nb(1), and one Co(1) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Ba(1), one Ba(2), one Mg(1), one Nb(1), and one Nb(2) atom.
Ba3MgNb2CoO9 crystallizes in the triclinic P1 space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(1), one O(3), one O(4), one O(6), one O(7), one O(9), two equivalent O(2), two equivalent O(5), and two equivalent O(8) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Nb(2)O6 octahedra, faces with three equivalent Nb(1)O6 octahedra, and faces with three equivalent Co(1)O6 octahedra. The Ba(1)-O(1) bond length is 3.26 Å. The Ba(1)-O(3) bond length is 3.08 Å. The Ba(1)-O(4) bond length is 2.97 Å. The Ba(1)-O(6) bond length is 2.91 Å. The Ba(1)-O(7) bond length is 3.11 Å. The Ba(1)-O(9) bond length is 3.27 Å. There is one shorter (3.09 Å) and one longer (3.11 Å) Ba(1)-O(2) bond length. There is one shorter (3.09 Å) and one longer (3.12 Å) Ba(1)-O(5) bond length. There is one shorter (2.98 Å) and one longer (2.99 Å) Ba(1)-O(8) bond length. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one Mg(1), one O(1), one O(2), one O(5), one O(6), one O(8), one O(9), and two equivalent O(4) atoms. The Ba(2)-Mg(1) bond length is 2.92 Å. The Ba(2)-O(1) bond length is 2.84 Å. The Ba(2)-O(2) bond length is 2.63 Å. The Ba(2)-O(5) bond length is 2.63 Å. The Ba(2)-O(6) bond length is 3.04 Å. The Ba(2)-O(8) bond length is 2.93 Å. The Ba(2)-O(9) bond length is 2.85 Å. There is one shorter (3.01 Å) and one longer (3.02 Å) Ba(2)-O(4) bond length. In the third Ba site, Ba(3) is bonded in a 9-coordinate geometry to one Mg(1), one O(2), one O(3), one O(4), one O(5), one O(7), one O(8), and two equivalent O(6) atoms. The Ba(3)-Mg(1) bond length is 2.94 Å. The Ba(3)-O(2) bond length is 2.75 Å. The Ba(3)-O(3) bond length is 2.64 Å. The Ba(3)-O(4) bond length is 2.94 Å. The Ba(3)-O(5) bond length is 2.75 Å. The Ba(3)-O(7) bond length is 2.65 Å. The Ba(3)-O(8) bond length is 3.09 Å. There is one shorter (3.09 Å) and one longer (3.13 Å) Ba(3)-O(6) bond length. Mg(1) is bonded in a rectangular see-saw-like geometry to one Ba(2), one Ba(3), one O(1), one O(3), one O(7), and one O(9) atom. The Mg(1)-O(1) bond length is 2.04 Å. The Mg(1)-O(3) bond length is 1.95 Å. The Mg(1)-O(7) bond length is 1.95 Å. The Mg(1)-O(9) bond length is 2.04 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(8), and one O(9) atom to form NbO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Co(1)O6 octahedra, and faces with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. The Nb(1)-O(1) bond length is 2.12 Å. The Nb(1)-O(2) bond length is 1.98 Å. The Nb(1)-O(4) bond length is 2.36 Å. The Nb(1)-O(5) bond length is 1.97 Å. The Nb(1)-O(8) bond length is 1.94 Å. The Nb(1)-O(9) bond length is 2.11 Å. In the second Nb site, Nb(2) is bonded to one O(1), one O(3), one O(4), one O(6), one O(7), and one O(9) atom to form NbO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Co(1)O6 octahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-8°. The Nb(2)-O(1) bond length is 2.10 Å. The Nb(2)-O(3) bond length is 2.06 Å. The Nb(2)-O(4) bond length is 2.38 Å. The Nb(2)-O(6) bond length is 1.92 Å. The Nb(2)-O(7) bond length is 2.06 Å. The Nb(2)-O(9) bond length is 2.10 Å. Co(1) is bonded to one O(2), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(2)O6 octahedra, and faces with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-6°. The Co(1)-O(2) bond length is 2.12 Å. The Co(1)-O(3) bond length is 2.17 Å. The Co(1)-O(5) bond length is 2.12 Å. The Co(1)-O(6) bond length is 2.66 Å. The Co(1)-O(7) bond length is 2.16 Å. The Co(1)-O(8) bond length is 2.55 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ba(1), one Ba(2), one Mg(1), one Nb(1), and one Nb(2) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Nb(1), and one Co(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(3), one Mg(1), one Nb(2), and one Co(1) atom. In the fourth O site, O(4) is bonded to one Ba(1), one Ba(3), two equivalent Ba(2), one Nb(1), and one Nb(2) atom to form distorted corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles are 22°. In the fifth O site, O(5) is bonded in a 6-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Nb(1), and one Co(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), two equivalent Ba(3), one Nb(2), and one Co(1) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(3), one Mg(1), one Nb(2), and one Co(1) atom. In the eighth O site, O(8) is bonded in a 1-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Nb(1), and one Co(1) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Ba(1), one Ba(2), one Mg(1), one Nb(1), and one Nb(2) atom.