CeNb3O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a 6-coordinate geometry to one O(10), one O(12), two equivalent O(2), and two equivalent O(7) atoms. In the second Ce site, Ce(2) is bonded in a 11-coordinate geometry to one O(1), one O(14), one O(15), one O(8), one O(9), two equivalent O(11), two equivalent O(3), and two equivalent O(6) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(13), one O(18), one O(2), one O(5), and one O(7) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. In the second Nb site, Nb(2) is bonded to one O(11), one O(14), one O(16), one O(3), one O(6), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 10-34°. In the third Nb site, Nb(3) is bonded to one O(1), one O(12), one O(15), one O(17), one O(4), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 6-29°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(10), one O(14), one O(18), one O(5), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 8-28°. In the fifth Nb site, Nb(5) is bonded to one O(12), one O(13), one O(16), one O(2), one O(4), and one O(7) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. In the sixth Nb site, Nb(6) is bonded to one O(11), one O(15), one O(17), one O(3), one O(6), and one O(9) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 6-34°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ce(2), one Nb(3), and one Nb(4) atom. In the second O site, O(2) is bonded to two equivalent Ce(1), one Nb(1), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing OCe2Nb2 trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ce(2), one Nb(2), and one Nb(6) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Nb(3) and one Nb(5) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Nb(1) and one Nb(4) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ce(2), one Nb(2), and one Nb(6) atom. In the seventh O site, O(7) is bonded to two equivalent Ce(1), one Nb(1), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing OCe2Nb2 tetrahedra. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ce(2), one Nb(2), and one Nb(4) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Ce(2), one Nb(3), and one Nb(6) atom. In the tenth O site, O(10) is bonded in a distorted T-shaped geometry to one Ce(1), one Nb(1), and one Nb(4) atom. In the eleventh O site, O(11) is bonded to two equivalent Ce(2), one Nb(2), and one Nb(6) atom to form distorted edge-sharing OCe2Nb2 tetrahedra. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Ce(1), one Nb(3), and one Nb(5) atom. In the thirteenth O site, O(13) is bonded in a linear geometry to one Nb(1) and one Nb(5) atom. In the fourteenth O site, O(14) is bonded in a distorted linear geometry to one Ce(2), one Nb(2), and one Nb(4) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Ce(2), one Nb(3), and one Nb(6) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(5) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Nb(3) and one Nb(6) atom. In the eighteenth O site, O(18) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom.
CeNb3O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a 6-coordinate geometry to one O(10), one O(12), two equivalent O(2), and two equivalent O(7) atoms. The Ce(1)-O(10) bond length is 2.53 Å. The Ce(1)-O(12) bond length is 2.53 Å. There is one shorter (2.32 Å) and one longer (2.45 Å) Ce(1)-O(2) bond length. Both Ce(1)-O(7) bond lengths are 2.52 Å. In the second Ce site, Ce(2) is bonded in a 11-coordinate geometry to one O(1), one O(14), one O(15), one O(8), one O(9), two equivalent O(11), two equivalent O(3), and two equivalent O(6) atoms. The Ce(2)-O(1) bond length is 2.63 Å. The Ce(2)-O(14) bond length is 2.91 Å. The Ce(2)-O(15) bond length is 2.90 Å. The Ce(2)-O(8) bond length is 2.58 Å. The Ce(2)-O(9) bond length is 2.56 Å. There is one shorter (2.47 Å) and one longer (2.50 Å) Ce(2)-O(11) bond length. There is one shorter (2.36 Å) and one longer (2.82 Å) Ce(2)-O(3) bond length. There is one shorter (2.70 Å) and one longer (2.72 Å) Ce(2)-O(6) bond length. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(13), one O(18), one O(2), one O(5), and one O(7) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. The Nb(1)-O(10) bond length is 2.01 Å. The Nb(1)-O(13) bond length is 2.01 Å. The Nb(1)-O(18) bond length is 1.88 Å. The Nb(1)-O(2) bond length is 2.22 Å. The Nb(1)-O(5) bond length is 1.96 Å. The Nb(1)-O(7) bond length is 2.09 Å. In the second Nb site, Nb(2) is bonded to one O(11), one O(14), one O(16), one O(3), one O(6), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 10-34°. The Nb(2)-O(11) bond length is 2.14 Å. The Nb(2)-O(14) bond length is 1.90 Å. The Nb(2)-O(16) bond length is 1.97 Å. The Nb(2)-O(3) bond length is 2.09 Å. The Nb(2)-O(6) bond length is 2.06 Å. The Nb(2)-O(8) bond length is 1.94 Å. In the third Nb site, Nb(3) is bonded to one O(1), one O(12), one O(15), one O(17), one O(4), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 6-29°. The Nb(3)-O(1) bond length is 2.05 Å. The Nb(3)-O(12) bond length is 2.02 Å. The Nb(3)-O(15) bond length is 2.01 Å. The Nb(3)-O(17) bond length is 1.97 Å. The Nb(3)-O(4) bond length is 1.99 Å. The Nb(3)-O(9) bond length is 2.02 Å. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(10), one O(14), one O(18), one O(5), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 8-28°. The Nb(4)-O(1) bond length is 1.98 Å. The Nb(4)-O(10) bond length is 2.01 Å. The Nb(4)-O(14) bond length is 2.02 Å. The Nb(4)-O(18) bond length is 2.02 Å. The Nb(4)-O(5) bond length is 1.98 Å. The Nb(4)-O(8) bond length is 2.05 Å. In the fifth Nb site, Nb(5) is bonded to one O(12), one O(13), one O(16), one O(2), one O(4), and one O(7) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 2-31°. The Nb(5)-O(12) bond length is 2.00 Å. The Nb(5)-O(13) bond length is 2.02 Å. The Nb(5)-O(16) bond length is 1.92 Å. The Nb(5)-O(2) bond length is 2.16 Å. The Nb(5)-O(4) bond length is 1.95 Å. The Nb(5)-O(7) bond length is 2.10 Å. In the sixth Nb site, Nb(6) is bonded to one O(11), one O(15), one O(17), one O(3), one O(6), and one O(9) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 6-34°. The Nb(6)-O(11) bond length is 2.12 Å. The Nb(6)-O(15) bond length is 1.92 Å. The Nb(6)-O(17) bond length is 1.93 Å. The Nb(6)-O(3) bond length is 2.17 Å. The Nb(6)-O(6) bond length is 2.02 Å. The Nb(6)-O(9) bond length is 1.98 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ce(2), one Nb(3), and one Nb(4) atom. In the second O site, O(2) is bonded to two equivalent Ce(1), one Nb(1), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing OCe2Nb2 trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ce(2), one Nb(2), and one Nb(6) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Nb(3) and one Nb(5) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Nb(1) and one Nb(4) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ce(2), one Nb(2), and one Nb(6) atom. In the seventh O site, O(7) is bonded to two equivalent Ce(1), one Nb(1), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing OCe2Nb2 tetrahedra. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ce(2), one Nb(2), and one Nb(4) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Ce(2), one Nb(3), and one Nb(6) atom. In the tenth O site, O(10) is bonded in a distorted T-shaped geometry to one Ce(1), one Nb(1), and one Nb(4) atom. In the eleventh O site, O(11) is bonded to two equivalent Ce(2), one Nb(2), and one Nb(6) atom to form distorted edge-sharing OCe2Nb2 tetrahedra. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Ce(1), one Nb(3), and one Nb(5) atom. In the thirteenth O site, O(13) is bonded in a linear geometry to one Nb(1) and one Nb(5) atom. In the fourteenth O site, O(14) is bonded in a distorted linear geometry to one Ce(2), one Nb(2), and one Nb(4) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Ce(2), one Nb(3), and one Nb(6) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(5) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Nb(3) and one Nb(6) atom. In the eighteenth O site, O(18) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom.