Co4Nb2O9 is Ilmenite-like structured and crystallizes in the triclinic P1 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(2)O6 octahedra, corners with three equivalent Co(4)O6 octahedra, corners with three equivalent Co(5)O6 octahedra, edges with three equivalent Co(6)O6 octahedra, and  a faceface with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(3)O6 octahedra, corners with three equivalent Co(6)O6 octahedra, edges with three equivalent Co(4)O6 octahedra, and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. In the third Nb site, Nb(3) is bonded to one O(1), one O(13), one O(14), one O(15), one O(2), and one O(3) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(2)O6 octahedra, corners with three equivalent Co(5)O6 octahedra, corners with three equivalent Co(8)O6 octahedra, edges with three equivalent Co(7)O6 octahedra, and  a faceface with one Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(16), one O(17), one O(18), one O(2), and one O(3) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(3)O6 octahedra, corners with three equivalent Co(7)O6 octahedra, edges with three equivalent Co(8)O6 octahedra, and  a faceface with one Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-58°. There are eight inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(10), one O(11), one O(12), one O(16), one O(17), and one O(18) atom to form CoO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Nb(4)O6 octahedra, corners with three equivalent Co(8)O6 octahedra, edges with three equivalent Co(3)O6 octahedra, and  a faceface with one Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-58°. In the second Co site, Co(2) is bonded to one O(13), one O(14), one O(15), one O(7), one O(8), and one O(9) atom to form CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, corners with three equivalent Co(6)O6 octahedra, edges with three equivalent Co(5)O6 octahedra, and  a faceface with one Co(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. In the third Co site, Co(3) is bonded to one O(10), one O(11), one O(12), one O(16), one O(17), and one O(18) atom to form CoO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Nb(4)O6 octahedra, corners with three equivalent Co(4)O6 octahedra, edges with three equivalent Co(1)O6 octahedra, and  a faceface with one Co(8)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. In the fourth Co site, Co(4) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Co(3)O6 octahedra, corners with three equivalent Co(6)O6 octahedra, edges with three equivalent Nb(2)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-66°. In the fifth Co site, Co(5) is bonded to one O(13), one O(14), one O(15), one O(7), one O(8), and one O(9) atom to form CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, corners with three equivalent Co(7)O6 octahedra, edges with three equivalent Co(2)O6 octahedra, and  a faceface with one Co(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. In the sixth Co site, Co(6) is bonded to one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Co(2)O6 octahedra, corners with three equivalent Co(4)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, and  a faceface with one Co(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-66°. In the seventh Co site, Co(7) is bonded to one O(1), one O(13), one O(14), one O(15), one O(2), and one O(3) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(4)O6 octahedra, corners with three equivalent Co(5)O6 octahedra, corners with three equivalent Co(8)O6 octahedra, edges with three equivalent Nb(3)O6 octahedra, and  a faceface with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-66°. In the eighth Co site, Co(8) is bonded to one O(1), one O(16), one O(17), one O(18), one O(2), and one O(3) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(3)O6 octahedra, corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(7)O6 octahedra, edges with three equivalent Nb(4)O6 octahedra, and  a faceface with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-66°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to one Nb(3), one Nb(4), one Co(7), and one Co(8) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid, and  an edgeedge with one O(17)NbCo3 trigonal pyramid. In the second O site, O(2) is bonded to one Nb(3), one Nb(4), one Co(7), and one Co(8) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(1)Nb2Co2 trigonal pyramid,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid,  an edgeedge with one O(14)NbCo3 trigonal pyramid, and  an edgeedge with one O(16)NbCo3 trigonal pyramid. In the third O site, O(3) is bonded to one Nb(3), one Nb(4), one Co(7), and one Co(8) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids,  an edgeedge with one O(1)Nb2Co2 trigonal pyramid,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(15)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Nb(1), one Nb(2), one Co(4), and one Co(6) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid, and  an edgeedge with one O(7)NbCo3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Nb(1), one Nb(2), one Co(4), and one Co(6) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid, and  an edgeedge with one O(8)NbCo3 trigonal pyramid. In the sixth O site, O(6) is bonded to one Nb(1), one Nb(2), one Co(4), and one Co(6) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the seventh O site, O(7) is bonded to one Nb(1), one Co(2), one Co(5), and one Co(6) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(8)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the eighth O site, O(8) is bonded to one Nb(1), one Co(2), one Co(5), and one Co(6) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(14)NbCo3 trigonal pyramid,  an edgeedge with one O(7)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the ninth O site, O(9) is bonded to one Nb(1), one Co(2), one Co(5), and one Co(6) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(15)NbCo3 trigonal pyramid,  an edgeedge with one O(7)NbCo3 trigonal pyramid, and  an edgeedge with one O(8)NbCo3 trigonal pyramid. In the tenth O site, O(10) is bonded to one Nb(2), one Co(1), one Co(3), and one Co(4) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid, and  an edgeedge with one O(16)NbCo3 trigonal pyramid. In the eleventh O site, O(11) is bonded to one Nb(2), one Co(1), one Co(3), and one Co(4) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid, and  an edgeedge with one O(17)NbCo3 trigonal pyramid. In the twelfth O site, O(12) is bonded to one Nb(2), one Co(1), one Co(3), and one Co(4) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one Nb(3), one Co(2), one Co(5), and one Co(7) atom. In the fourteenth O site, O(14) is bonded to one Nb(3), one Co(2), one Co(5), and one Co(7) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(15)NbCo3 trigonal pyramid, and  an edgeedge with one O(8)NbCo3 trigonal pyramid. In the fifteenth O site, O(15) is bonded to one Nb(3), one Co(2), one Co(5), and one Co(7) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid,  an edgeedge with one O(14)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the sixteenth O site, O(16) is bonded to one Nb(4), one Co(1), one Co(3), and one Co(8) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid,  an edgeedge with one O(17)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the seventeenth O site, O(17) is bonded to one Nb(4), one Co(1), one Co(3), and one Co(8) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(1)Nb2Co2 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid,  an edgeedge with one O(16)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the eighteenth O site, O(18) is bonded to one Nb(4), one Co(1), one Co(3), and one Co(8) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid,  an edgeedge with one O(16)NbCo3 trigonal pyramid, and  an edgeedge with one O(17)NbCo3 trigonal pyramid.
Co4Nb2O9 is Ilmenite-like structured and crystallizes in the triclinic P1 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(2)O6 octahedra, corners with three equivalent Co(4)O6 octahedra, corners with three equivalent Co(5)O6 octahedra, edges with three equivalent Co(6)O6 octahedra, and  a faceface with one Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. The Nb(1)-O(4) bond length is 2.20 Å. The Nb(1)-O(5) bond length is 2.14 Å. The Nb(1)-O(6) bond length is 2.15 Å. The Nb(1)-O(7) bond length is 1.93 Å. The Nb(1)-O(8) bond length is 1.92 Å. The Nb(1)-O(9) bond length is 1.94 Å. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(3)O6 octahedra, corners with three equivalent Co(6)O6 octahedra, edges with three equivalent Co(4)O6 octahedra, and  a faceface with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. The Nb(2)-O(10) bond length is 1.92 Å. The Nb(2)-O(11) bond length is 1.92 Å. The Nb(2)-O(12) bond length is 1.93 Å. The Nb(2)-O(4) bond length is 2.16 Å. The Nb(2)-O(5) bond length is 2.17 Å. The Nb(2)-O(6) bond length is 2.17 Å. In the third Nb site, Nb(3) is bonded to one O(1), one O(13), one O(14), one O(15), one O(2), and one O(3) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(2)O6 octahedra, corners with three equivalent Co(5)O6 octahedra, corners with three equivalent Co(8)O6 octahedra, edges with three equivalent Co(7)O6 octahedra, and  a faceface with one Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. The Nb(3)-O(1) bond length is 2.18 Å. The Nb(3)-O(13) bond length is 1.92 Å. The Nb(3)-O(14) bond length is 1.92 Å. The Nb(3)-O(15) bond length is 1.94 Å. The Nb(3)-O(2) bond length is 2.15 Å. The Nb(3)-O(3) bond length is 2.17 Å. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(16), one O(17), one O(18), one O(2), and one O(3) atom to form distorted NbO6 octahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(3)O6 octahedra, corners with three equivalent Co(7)O6 octahedra, edges with three equivalent Co(8)O6 octahedra, and  a faceface with one Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-58°. The Nb(4)-O(1) bond length is 2.15 Å. The Nb(4)-O(16) bond length is 1.93 Å. The Nb(4)-O(17) bond length is 1.92 Å. The Nb(4)-O(18) bond length is 1.93 Å. The Nb(4)-O(2) bond length is 2.18 Å. The Nb(4)-O(3) bond length is 2.16 Å. There are eight inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(10), one O(11), one O(12), one O(16), one O(17), and one O(18) atom to form CoO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Nb(4)O6 octahedra, corners with three equivalent Co(8)O6 octahedra, edges with three equivalent Co(3)O6 octahedra, and  a faceface with one Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-58°. The Co(1)-O(10) bond length is 2.15 Å. The Co(1)-O(11) bond length is 2.19 Å. The Co(1)-O(12) bond length is 2.15 Å. The Co(1)-O(16) bond length is 2.10 Å. The Co(1)-O(17) bond length is 2.08 Å. The Co(1)-O(18) bond length is 2.08 Å. In the second Co site, Co(2) is bonded to one O(13), one O(14), one O(15), one O(7), one O(8), and one O(9) atom to form CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, corners with three equivalent Co(6)O6 octahedra, edges with three equivalent Co(5)O6 octahedra, and  a faceface with one Co(7)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. The Co(2)-O(13) bond length is 2.14 Å. The Co(2)-O(14) bond length is 2.16 Å. The Co(2)-O(15) bond length is 2.13 Å. The Co(2)-O(7) bond length is 2.09 Å. The Co(2)-O(8) bond length is 2.11 Å. The Co(2)-O(9) bond length is 2.10 Å. In the third Co site, Co(3) is bonded to one O(10), one O(11), one O(12), one O(16), one O(17), and one O(18) atom to form CoO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Nb(4)O6 octahedra, corners with three equivalent Co(4)O6 octahedra, edges with three equivalent Co(1)O6 octahedra, and  a faceface with one Co(8)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. The Co(3)-O(10) bond length is 2.10 Å. The Co(3)-O(11) bond length is 2.08 Å. The Co(3)-O(12) bond length is 2.10 Å. The Co(3)-O(16) bond length is 2.14 Å. The Co(3)-O(17) bond length is 2.17 Å. The Co(3)-O(18) bond length is 2.15 Å. In the fourth Co site, Co(4) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Co(3)O6 octahedra, corners with three equivalent Co(6)O6 octahedra, edges with three equivalent Nb(2)O6 octahedra, and  a faceface with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-66°. The Co(4)-O(10) bond length is 2.33 Å. The Co(4)-O(11) bond length is 2.29 Å. The Co(4)-O(12) bond length is 2.31 Å. The Co(4)-O(4) bond length is 2.02 Å. The Co(4)-O(5) bond length is 2.03 Å. The Co(4)-O(6) bond length is 2.02 Å. In the fifth Co site, Co(5) is bonded to one O(13), one O(14), one O(15), one O(7), one O(8), and one O(9) atom to form CoO6 octahedra that share corners with three equivalent Nb(1)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, corners with three equivalent Co(7)O6 octahedra, edges with three equivalent Co(2)O6 octahedra, and  a faceface with one Co(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-57°. The Co(5)-O(13) bond length is 2.08 Å. The Co(5)-O(14) bond length is 2.10 Å. The Co(5)-O(15) bond length is 2.12 Å. The Co(5)-O(7) bond length is 2.15 Å. The Co(5)-O(8) bond length is 2.15 Å. The Co(5)-O(9) bond length is 2.16 Å. In the sixth Co site, Co(6) is bonded to one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(2)O6 octahedra, corners with three equivalent Co(2)O6 octahedra, corners with three equivalent Co(4)O6 octahedra, edges with three equivalent Nb(1)O6 octahedra, and  a faceface with one Co(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-66°. The Co(6)-O(4) bond length is 2.03 Å. The Co(6)-O(5) bond length is 2.05 Å. The Co(6)-O(6) bond length is 2.04 Å. The Co(6)-O(7) bond length is 2.30 Å. The Co(6)-O(8) bond length is 2.27 Å. The Co(6)-O(9) bond length is 2.22 Å. In the seventh Co site, Co(7) is bonded to one O(1), one O(13), one O(14), one O(15), one O(2), and one O(3) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(4)O6 octahedra, corners with three equivalent Co(5)O6 octahedra, corners with three equivalent Co(8)O6 octahedra, edges with three equivalent Nb(3)O6 octahedra, and  a faceface with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-66°. The Co(7)-O(1) bond length is 2.02 Å. The Co(7)-O(13) bond length is 2.33 Å. The Co(7)-O(14) bond length is 2.29 Å. The Co(7)-O(15) bond length is 2.27 Å. The Co(7)-O(2) bond length is 2.03 Å. The Co(7)-O(3) bond length is 2.02 Å. In the eighth Co site, Co(8) is bonded to one O(1), one O(16), one O(17), one O(18), one O(2), and one O(3) atom to form distorted CoO6 octahedra that share corners with three equivalent Nb(3)O6 octahedra, corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(7)O6 octahedra, edges with three equivalent Nb(4)O6 octahedra, and  a faceface with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-66°. The Co(8)-O(1) bond length is 2.03 Å. The Co(8)-O(16) bond length is 2.29 Å. The Co(8)-O(17) bond length is 2.28 Å. The Co(8)-O(18) bond length is 2.30 Å. The Co(8)-O(2) bond length is 2.03 Å. The Co(8)-O(3) bond length is 2.02 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to one Nb(3), one Nb(4), one Co(7), and one Co(8) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid, and  an edgeedge with one O(17)NbCo3 trigonal pyramid. In the second O site, O(2) is bonded to one Nb(3), one Nb(4), one Co(7), and one Co(8) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(1)Nb2Co2 trigonal pyramid,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid,  an edgeedge with one O(14)NbCo3 trigonal pyramid, and  an edgeedge with one O(16)NbCo3 trigonal pyramid. In the third O site, O(3) is bonded to one Nb(3), one Nb(4), one Co(7), and one Co(8) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids,  an edgeedge with one O(1)Nb2Co2 trigonal pyramid,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(15)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Nb(1), one Nb(2), one Co(4), and one Co(6) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid, and  an edgeedge with one O(7)NbCo3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Nb(1), one Nb(2), one Co(4), and one Co(6) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid, and  an edgeedge with one O(8)NbCo3 trigonal pyramid. In the sixth O site, O(6) is bonded to one Nb(1), one Nb(2), one Co(4), and one Co(6) atom to form distorted ONb2Co2 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the seventh O site, O(7) is bonded to one Nb(1), one Co(2), one Co(5), and one Co(6) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(8)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the eighth O site, O(8) is bonded to one Nb(1), one Co(2), one Co(5), and one Co(6) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(14)NbCo3 trigonal pyramid,  an edgeedge with one O(7)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the ninth O site, O(9) is bonded to one Nb(1), one Co(2), one Co(5), and one Co(6) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(15)NbCo3 trigonal pyramid,  an edgeedge with one O(7)NbCo3 trigonal pyramid, and  an edgeedge with one O(8)NbCo3 trigonal pyramid. In the tenth O site, O(10) is bonded to one Nb(2), one Co(1), one Co(3), and one Co(4) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(5)Nb2Co2 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid, and  an edgeedge with one O(16)NbCo3 trigonal pyramid. In the eleventh O site, O(11) is bonded to one Nb(2), one Co(1), one Co(3), and one Co(4) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(6)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(4)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid, and  an edgeedge with one O(17)NbCo3 trigonal pyramid. In the twelfth O site, O(12) is bonded to one Nb(2), one Co(1), one Co(3), and one Co(4) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(4)Nb2Co2 trigonal pyramids, corners with two equivalent O(5)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids,  an edgeedge with one O(6)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one Nb(3), one Co(2), one Co(5), and one Co(7) atom. In the fourteenth O site, O(14) is bonded to one Nb(3), one Co(2), one Co(5), and one Co(7) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(15)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(9)NbCo3 trigonal pyramids,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(15)NbCo3 trigonal pyramid, and  an edgeedge with one O(8)NbCo3 trigonal pyramid. In the fifteenth O site, O(15) is bonded to one Nb(3), one Co(2), one Co(5), and one Co(7) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(14)NbCo3 trigonal pyramids, corners with two equivalent O(7)NbCo3 trigonal pyramids, corners with two equivalent O(8)NbCo3 trigonal pyramids,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid,  an edgeedge with one O(14)NbCo3 trigonal pyramid, and  an edgeedge with one O(9)NbCo3 trigonal pyramid. In the sixteenth O site, O(16) is bonded to one Nb(4), one Co(1), one Co(3), and one Co(8) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(2)Nb2Co2 trigonal pyramid,  an edgeedge with one O(10)NbCo3 trigonal pyramid,  an edgeedge with one O(17)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the seventeenth O site, O(17) is bonded to one Nb(4), one Co(1), one Co(3), and one Co(8) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(3)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(12)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(18)NbCo3 trigonal pyramids,  an edgeedge with one O(1)Nb2Co2 trigonal pyramid,  an edgeedge with one O(11)NbCo3 trigonal pyramid,  an edgeedge with one O(16)NbCo3 trigonal pyramid, and  an edgeedge with one O(18)NbCo3 trigonal pyramid. In the eighteenth O site, O(18) is bonded to one Nb(4), one Co(1), one Co(3), and one Co(8) atom to form distorted ONbCo3 trigonal pyramids that share corners with two equivalent O(1)Nb2Co2 trigonal pyramids, corners with two equivalent O(2)Nb2Co2 trigonal pyramids, corners with two equivalent O(10)NbCo3 trigonal pyramids, corners with two equivalent O(11)NbCo3 trigonal pyramids, corners with two equivalent O(16)NbCo3 trigonal pyramids, corners with two equivalent O(17)NbCo3 trigonal pyramids,  an edgeedge with one O(3)Nb2Co2 trigonal pyramid,  an edgeedge with one O(12)NbCo3 trigonal pyramid,  an edgeedge with one O(16)NbCo3 trigonal pyramid, and  an edgeedge with one O(17)NbCo3 trigonal pyramid.