NdNb3O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(14), one O(15), two equivalent O(18), and two equivalent O(6) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one O(16), one O(17), one O(4), one O(5), two equivalent O(12), and two equivalent O(13) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(11), one O(15), one O(18), one O(6), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-32°. In the second Nb site, Nb(2) is bonded to one O(12), one O(13), one O(17), one O(2), one O(4), and one O(8) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-31°. In the third Nb site, Nb(3) is bonded to one O(10), one O(14), one O(16), one O(3), one O(5), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 12-28°. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(10), one O(15), one O(17), one O(4), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-31°. In the fifth Nb site, Nb(5) is bonded to one O(12), one O(13), one O(16), one O(2), one O(5), and one O(9) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-28°. In the sixth Nb site, Nb(6) is bonded to one O(11), one O(14), one O(18), 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 14-32°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the second O site, O(2) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the third O site, O(3) is bonded in a distorted linear geometry to one Nb(3) and one Nb(6) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Nd(2), one Nb(2), and one Nb(4) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Nd(2), one Nb(3), and one Nb(5) atom. In the sixth O site, O(6) is bonded to two equivalent Nd(1), one Nb(1), and one Nb(6) atom to form distorted edge-sharing ONd2Nb2 tetrahedra. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(6) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(3) and one Nb(5) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Nd(1), one Nb(3), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nd(1), one Nb(1), and one Nb(6) atom. In the twelfth O site, O(12) is bonded to two equivalent Nd(2), one Nb(2), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing ONd2Nb2 trigonal pyramids. In the thirteenth O site, O(13) is bonded to two equivalent Nd(2), one Nb(2), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing ONd2Nb2 trigonal pyramids. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Nd(1), one Nb(3), and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a distorted T-shaped geometry to one Nd(1), one Nb(1), and one Nb(4) atom. In the sixteenth O site, O(16) is bonded in a distorted T-shaped geometry to one Nd(2), one Nb(3), and one Nb(5) atom. In the seventeenth O site, O(17) is bonded in a distorted T-shaped geometry to one Nd(2), one Nb(2), and one Nb(4) atom. In the eighteenth O site, O(18) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Nd(1), one Nb(1), and one Nb(6) atom.
NdNb3O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(14), one O(15), two equivalent O(18), and two equivalent O(6) atoms. The Nd(1)-O(10) bond length is 2.52 Å. The Nd(1)-O(11) bond length is 2.48 Å. The Nd(1)-O(14) bond length is 2.64 Å. The Nd(1)-O(15) bond length is 2.60 Å. There is one shorter (2.63 Å) and one longer (2.67 Å) Nd(1)-O(18) bond length. There is one shorter (2.45 Å) and one longer (2.49 Å) Nd(1)-O(6) bond length. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one O(16), one O(17), one O(4), one O(5), two equivalent O(12), and two equivalent O(13) atoms. The Nd(2)-O(16) bond length is 2.68 Å. The Nd(2)-O(17) bond length is 2.65 Å. The Nd(2)-O(4) bond length is 2.53 Å. The Nd(2)-O(5) bond length is 2.54 Å. There is one shorter (2.40 Å) and one longer (2.41 Å) Nd(2)-O(12) bond length. There is one shorter (2.56 Å) and one longer (2.57 Å) Nd(2)-O(13) bond length. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(11), one O(15), one O(18), one O(6), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-32°. The Nb(1)-O(1) bond length is 1.92 Å. The Nb(1)-O(11) bond length is 2.14 Å. The Nb(1)-O(15) bond length is 1.99 Å. The Nb(1)-O(18) bond length is 2.02 Å. The Nb(1)-O(6) bond length is 2.09 Å. The Nb(1)-O(7) bond length is 1.94 Å. In the second Nb site, Nb(2) is bonded to one O(12), one O(13), one O(17), one O(2), one O(4), and one O(8) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-31°. The Nb(2)-O(12) bond length is 2.16 Å. The Nb(2)-O(13) bond length is 2.10 Å. The Nb(2)-O(17) bond length is 1.95 Å. The Nb(2)-O(2) bond length is 2.01 Å. The Nb(2)-O(4) bond length is 2.01 Å. The Nb(2)-O(8) bond length is 1.89 Å. In the third Nb site, Nb(3) is bonded to one O(10), one O(14), one O(16), one O(3), one O(5), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 12-28°. The Nb(3)-O(10) bond length is 1.96 Å. The Nb(3)-O(14) bond length is 2.04 Å. The Nb(3)-O(16) bond length is 1.98 Å. The Nb(3)-O(3) bond length is 2.03 Å. The Nb(3)-O(5) bond length is 1.98 Å. The Nb(3)-O(9) bond length is 2.03 Å. In the fourth Nb site, Nb(4) is bonded to one O(1), one O(10), one O(15), one O(17), one O(4), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-31°. The Nb(4)-O(1) bond length is 2.01 Å. The Nb(4)-O(10) bond length is 2.10 Å. The Nb(4)-O(15) bond length is 2.00 Å. The Nb(4)-O(17) bond length is 2.01 Å. The Nb(4)-O(4) bond length is 1.99 Å. The Nb(4)-O(7) bond length is 1.93 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(5), and one O(9) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-28°. The Nb(5)-O(12) bond length is 2.20 Å. The Nb(5)-O(13) bond length is 2.07 Å. The Nb(5)-O(16) bond length is 1.97 Å. The Nb(5)-O(2) bond length is 2.00 Å. The Nb(5)-O(5) bond length is 2.02 Å. The Nb(5)-O(9) bond length is 1.88 Å. In the sixth Nb site, Nb(6) is bonded to one O(11), one O(14), one O(18), 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 14-32°. The Nb(6)-O(11) bond length is 2.03 Å. The Nb(6)-O(14) bond length is 1.93 Å. The Nb(6)-O(18) bond length is 2.10 Å. The Nb(6)-O(3) bond length is 1.89 Å. The Nb(6)-O(6) bond length is 2.15 Å. The Nb(6)-O(8) bond length is 2.00 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the second O site, O(2) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the third O site, O(3) is bonded in a distorted linear geometry to one Nb(3) and one Nb(6) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Nd(2), one Nb(2), and one Nb(4) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Nd(2), one Nb(3), and one Nb(5) atom. In the sixth O site, O(6) is bonded to two equivalent Nd(1), one Nb(1), and one Nb(6) atom to form distorted edge-sharing ONd2Nb2 tetrahedra. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(6) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(3) and one Nb(5) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Nd(1), one Nb(3), and one Nb(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nd(1), one Nb(1), and one Nb(6) atom. In the twelfth O site, O(12) is bonded to two equivalent Nd(2), one Nb(2), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing ONd2Nb2 trigonal pyramids. In the thirteenth O site, O(13) is bonded to two equivalent Nd(2), one Nb(2), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing ONd2Nb2 trigonal pyramids. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Nd(1), one Nb(3), and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a distorted T-shaped geometry to one Nd(1), one Nb(1), and one Nb(4) atom. In the sixteenth O site, O(16) is bonded in a distorted T-shaped geometry to one Nd(2), one Nb(3), and one Nb(5) atom. In the seventeenth O site, O(17) is bonded in a distorted T-shaped geometry to one Nd(2), one Nb(2), and one Nb(4) atom. In the eighteenth O site, O(18) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Nd(1), one Nb(1), and one Nb(6) atom.