LaNb3O9 crystallizes in the monoclinic Cm space group. There are two inequivalent La sites. In the first La site, La(1) is bonded to one O(1), one O(3), two equivalent O(10), two equivalent O(2), two equivalent O(4), two equivalent O(7), and two equivalent O(8) atoms to form LaO12 cuboctahedra that share  a cornercorner with one La(2)O12 cuboctahedra, corners with two equivalent La(1)O12 cuboctahedra, faces with two equivalent La(2)O12 cuboctahedra,  a faceface with one Nb(1)O6 octahedra,  a faceface with one Nb(3)O6 octahedra,  a faceface with one Nb(5)O6 octahedra,  a faceface with one Nb(6)O6 octahedra, faces with two equivalent Nb(2)O6 octahedra, and faces with two equivalent Nb(4)O6 octahedra. In the second La site, La(2) is bonded to one O(1), one O(4), two equivalent O(10), two equivalent O(12), two equivalent O(3), two equivalent O(7), and two equivalent O(9) atoms to form LaO12 cuboctahedra that share  a cornercorner with one La(1)O12 cuboctahedra, corners with two equivalent La(2)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra,  a faceface with one Nb(1)O6 octahedra,  a faceface with one Nb(2)O6 octahedra,  a faceface with one Nb(4)O6 octahedra,  a faceface with one Nb(6)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, and faces with two equivalent Nb(5)O6 octahedra. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(6), two equivalent O(12), and two equivalent O(8) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and  a faceface with one La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-15°. In the second Nb site, Nb(2) is bonded to one O(4), one O(6), two equivalent O(2), and two equivalent O(7) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra,  a faceface with one La(2)O12 cuboctahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-17°. In the third Nb site, Nb(3) is bonded to one O(3), one O(5), two equivalent O(7), and two equivalent O(9) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and faces with two equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-17°. In the fourth Nb site, Nb(4) is bonded to one O(4), one O(5), two equivalent O(10), and two equivalent O(8) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra,  a faceface with one La(2)O12 cuboctahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-18°. In the fifth Nb site, Nb(5) is bonded to one O(11), one O(3), two equivalent O(10), and two equivalent O(12) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and faces with two equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-18°. In the sixth Nb site, Nb(6) is bonded to one O(1), one O(11), two equivalent O(2), and two equivalent O(9) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and  a faceface with one La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-13°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one La(1), one La(2), one Nb(1), and one Nb(6) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one La(1), one Nb(2), and one Nb(6) atom. In the third O site, O(3) is bonded to one La(1), two equivalent La(2), one Nb(3), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing OLa3Nb2 square pyramids. In the fourth O site, O(4) is bonded to one La(2), two equivalent La(1), one Nb(2), and one Nb(4) atom to form a mixture of distorted corner and edge-sharing OLa3Nb2 square pyramids. In the fifth O site, O(5) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one La(1), one La(2), one Nb(2), and one Nb(3) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one La(1), one Nb(1), and one Nb(4) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one La(2), one Nb(3), and one Nb(6) atom. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to one La(1), one La(2), one Nb(4), and one Nb(5) atom. In the eleventh O site, O(11) is bonded in a linear geometry to one Nb(5) and one Nb(6) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one La(2), one Nb(1), and one Nb(5) atom.
LaNb3O9 crystallizes in the monoclinic Cm space group. There are two inequivalent La sites. In the first La site, La(1) is bonded to one O(1), one O(3), two equivalent O(10), two equivalent O(2), two equivalent O(4), two equivalent O(7), and two equivalent O(8) atoms to form LaO12 cuboctahedra that share  a cornercorner with one La(2)O12 cuboctahedra, corners with two equivalent La(1)O12 cuboctahedra, faces with two equivalent La(2)O12 cuboctahedra,  a faceface with one Nb(1)O6 octahedra,  a faceface with one Nb(3)O6 octahedra,  a faceface with one Nb(5)O6 octahedra,  a faceface with one Nb(6)O6 octahedra, faces with two equivalent Nb(2)O6 octahedra, and faces with two equivalent Nb(4)O6 octahedra. The La(1)-O(1) bond length is 2.88 Å. The La(1)-O(3) bond length is 2.60 Å. Both La(1)-O(10) bond lengths are 2.64 Å. Both La(1)-O(2) bond lengths are 2.69 Å. Both La(1)-O(4) bond lengths are 2.81 Å. Both La(1)-O(7) bond lengths are 2.66 Å. Both La(1)-O(8) bond lengths are 2.69 Å. In the second La site, La(2) is bonded to one O(1), one O(4), two equivalent O(10), two equivalent O(12), two equivalent O(3), two equivalent O(7), and two equivalent O(9) atoms to form LaO12 cuboctahedra that share  a cornercorner with one La(1)O12 cuboctahedra, corners with two equivalent La(2)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra,  a faceface with one Nb(1)O6 octahedra,  a faceface with one Nb(2)O6 octahedra,  a faceface with one Nb(4)O6 octahedra,  a faceface with one Nb(6)O6 octahedra, faces with two equivalent Nb(3)O6 octahedra, and faces with two equivalent Nb(5)O6 octahedra. The La(2)-O(1) bond length is 2.86 Å. The La(2)-O(4) bond length is 2.66 Å. Both La(2)-O(10) bond lengths are 2.67 Å. Both La(2)-O(12) bond lengths are 2.67 Å. Both La(2)-O(3) bond lengths are 2.81 Å. Both La(2)-O(7) bond lengths are 2.67 Å. Both La(2)-O(9) bond lengths are 2.68 Å. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(6), two equivalent O(12), and two equivalent O(8) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and  a faceface with one La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-15°. The Nb(1)-O(1) bond length is 2.03 Å. The Nb(1)-O(6) bond length is 1.97 Å. Both Nb(1)-O(12) bond lengths are 1.99 Å. Both Nb(1)-O(8) bond lengths are 2.00 Å. In the second Nb site, Nb(2) is bonded to one O(4), one O(6), two equivalent O(2), and two equivalent O(7) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra,  a faceface with one La(2)O12 cuboctahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-17°. The Nb(2)-O(4) bond length is 2.15 Å. The Nb(2)-O(6) bond length is 1.92 Å. Both Nb(2)-O(2) bond lengths are 2.00 Å. Both Nb(2)-O(7) bond lengths are 1.99 Å. In the third Nb site, Nb(3) is bonded to one O(3), one O(5), two equivalent O(7), and two equivalent O(9) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(6)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and faces with two equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-17°. The Nb(3)-O(3) bond length is 2.07 Å. The Nb(3)-O(5) bond length is 1.95 Å. Both Nb(3)-O(7) bond lengths are 2.12 Å. Both Nb(3)-O(9) bond lengths are 1.94 Å. In the fourth Nb site, Nb(4) is bonded to one O(4), one O(5), two equivalent O(10), and two equivalent O(8) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra,  a faceface with one La(2)O12 cuboctahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-18°. The Nb(4)-O(4) bond length is 2.09 Å. The Nb(4)-O(5) bond length is 1.93 Å. Both Nb(4)-O(10) bond lengths are 2.09 Å. Both Nb(4)-O(8) bond lengths are 1.96 Å. In the fifth Nb site, Nb(5) is bonded to one O(11), one O(3), two equivalent O(10), and two equivalent O(12) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(6)O6 octahedra, corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(4)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and faces with two equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-18°. The Nb(5)-O(11) bond length is 1.89 Å. The Nb(5)-O(3) bond length is 2.17 Å. Both Nb(5)-O(10) bond lengths are 2.03 Å. Both Nb(5)-O(12) bond lengths are 1.98 Å. In the sixth Nb site, Nb(6) is bonded to one O(1), one O(11), two equivalent O(2), and two equivalent O(9) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, and  a faceface with one La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-13°. The Nb(6)-O(1) bond length is 2.00 Å. The Nb(6)-O(11) bond length is 2.00 Å. Both Nb(6)-O(2) bond lengths are 1.95 Å. Both Nb(6)-O(9) bond lengths are 2.03 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one La(1), one La(2), one Nb(1), and one Nb(6) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one La(1), one Nb(2), and one Nb(6) atom. In the third O site, O(3) is bonded to one La(1), two equivalent La(2), one Nb(3), and one Nb(5) atom to form a mixture of distorted corner and edge-sharing OLa3Nb2 square pyramids. In the fourth O site, O(4) is bonded to one La(2), two equivalent La(1), one Nb(2), and one Nb(4) atom to form a mixture of distorted corner and edge-sharing OLa3Nb2 square pyramids. In the fifth O site, O(5) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one La(1), one La(2), one Nb(2), and one Nb(3) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one La(1), one Nb(1), and one Nb(4) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one La(2), one Nb(3), and one Nb(6) atom. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to one La(1), one La(2), one Nb(4), and one Nb(5) atom. In the eleventh O site, O(11) is bonded in a linear geometry to one Nb(5) and one Nb(6) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one La(2), one Nb(1), and one Nb(5) atom.