Bi3NbO7 crystallizes in the monoclinic Cm space group. Nb(1) is bonded in a 5-coordinate geometry to one O(1), one O(6), two equivalent O(4), and three equivalent O(2) atoms. There are three inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(3), one O(5), and three equivalent O(7) atoms to form corner-sharing BiO5 trigonal bipyramids. In the second Bi site, Bi(2) is bonded in a 7-coordinate geometry to one O(4), three equivalent O(1), and three equivalent O(3) atoms. In the third Bi site, Bi(3) is bonded in a 7-coordinate geometry to one O(2), three equivalent O(5), and three equivalent O(6) atoms. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Nb(1) and three equivalent Bi(2) atoms to form distorted ONbBi3 tetrahedra that share  a cornercorner with one O(6)NbBi3 tetrahedra, corners with three equivalent O(3)Bi4 tetrahedra, corners with three equivalent O(2)Nb3Bi tetrahedra, corners with six equivalent O(1)NbBi3 tetrahedra, and edges with three equivalent O(3)Bi4 tetrahedra. In the second O site, O(2) is bonded to three equivalent Nb(1) and one Bi(3) atom to form distorted ONb3Bi tetrahedra that share corners with three equivalent O(5)Bi4 tetrahedra, corners with three equivalent O(1)NbBi3 tetrahedra, corners with six equivalent O(2)Nb3Bi tetrahedra, and edges with three equivalent O(6)NbBi3 tetrahedra. In the third O site, O(3) is bonded to one Bi(1) and three equivalent Bi(2) atoms to form OBi4 tetrahedra that share  a cornercorner with one O(5)Bi4 tetrahedra, corners with three equivalent O(1)NbBi3 tetrahedra, corners with six equivalent O(3)Bi4 tetrahedra, and edges with three equivalent O(1)NbBi3 tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Nb(1) and one Bi(2) atom. In the fifth O site, O(5) is bonded to one Bi(1) and three equivalent Bi(3) atoms to form OBi4 tetrahedra that share  a cornercorner with one O(3)Bi4 tetrahedra, corners with three equivalent O(2)Nb3Bi tetrahedra, corners with three equivalent O(6)NbBi3 tetrahedra, corners with six equivalent O(5)Bi4 tetrahedra, and edges with three equivalent O(6)NbBi3 tetrahedra. In the sixth O site, O(6) is bonded to one Nb(1) and three equivalent Bi(3) atoms to form distorted ONbBi3 tetrahedra that share  a cornercorner with one O(1)NbBi3 tetrahedra, corners with three equivalent O(5)Bi4 tetrahedra, corners with six equivalent O(6)NbBi3 tetrahedra, edges with three equivalent O(5)Bi4 tetrahedra, and edges with three equivalent O(2)Nb3Bi tetrahedra. In the seventh O site, O(7) is bonded in a trigonal planar geometry to three equivalent Bi(1) atoms.
Bi3NbO7 crystallizes in the monoclinic Cm space group. Nb(1) is bonded in a 5-coordinate geometry to one O(1), one O(6), two equivalent O(4), and three equivalent O(2) atoms. The Nb(1)-O(1) bond length is 2.02 Å. The Nb(1)-O(6) bond length is 1.97 Å. Both Nb(1)-O(4) bond lengths are 2.09 Å. There is one shorter (1.99 Å) and two longer (2.48 Å) Nb(1)-O(2) bond lengths. There are three inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(3), one O(5), and three equivalent O(7) atoms to form corner-sharing BiO5 trigonal bipyramids. The Bi(1)-O(3) bond length is 2.40 Å. The Bi(1)-O(5) bond length is 2.33 Å. There are two shorter (2.25 Å) and one longer (2.27 Å) Bi(1)-O(7) bond length. In the second Bi site, Bi(2) is bonded in a 7-coordinate geometry to one O(4), three equivalent O(1), and three equivalent O(3) atoms. The Bi(2)-O(4) bond length is 2.41 Å. There is one shorter (2.36 Å) and two longer (2.49 Å) Bi(2)-O(1) bond lengths. There are two shorter (2.41 Å) and one longer (2.69 Å) Bi(2)-O(3) bond length. In the third Bi site, Bi(3) is bonded in a 7-coordinate geometry to one O(2), three equivalent O(5), and three equivalent O(6) atoms. The Bi(3)-O(2) bond length is 2.46 Å. There are two shorter (2.42 Å) and one longer (2.49 Å) Bi(3)-O(5) bond length. There are two shorter (2.44 Å) and one longer (2.47 Å) Bi(3)-O(6) bond length. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Nb(1) and three equivalent Bi(2) atoms to form distorted ONbBi3 tetrahedra that share  a cornercorner with one O(6)NbBi3 tetrahedra, corners with three equivalent O(3)Bi4 tetrahedra, corners with three equivalent O(2)Nb3Bi tetrahedra, corners with six equivalent O(1)NbBi3 tetrahedra, and edges with three equivalent O(3)Bi4 tetrahedra. In the second O site, O(2) is bonded to three equivalent Nb(1) and one Bi(3) atom to form distorted ONb3Bi tetrahedra that share corners with three equivalent O(5)Bi4 tetrahedra, corners with three equivalent O(1)NbBi3 tetrahedra, corners with six equivalent O(2)Nb3Bi tetrahedra, and edges with three equivalent O(6)NbBi3 tetrahedra. In the third O site, O(3) is bonded to one Bi(1) and three equivalent Bi(2) atoms to form OBi4 tetrahedra that share  a cornercorner with one O(5)Bi4 tetrahedra, corners with three equivalent O(1)NbBi3 tetrahedra, corners with six equivalent O(3)Bi4 tetrahedra, and edges with three equivalent O(1)NbBi3 tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Nb(1) and one Bi(2) atom. In the fifth O site, O(5) is bonded to one Bi(1) and three equivalent Bi(3) atoms to form OBi4 tetrahedra that share  a cornercorner with one O(3)Bi4 tetrahedra, corners with three equivalent O(2)Nb3Bi tetrahedra, corners with three equivalent O(6)NbBi3 tetrahedra, corners with six equivalent O(5)Bi4 tetrahedra, and edges with three equivalent O(6)NbBi3 tetrahedra. In the sixth O site, O(6) is bonded to one Nb(1) and three equivalent Bi(3) atoms to form distorted ONbBi3 tetrahedra that share  a cornercorner with one O(1)NbBi3 tetrahedra, corners with three equivalent O(5)Bi4 tetrahedra, corners with six equivalent O(6)NbBi3 tetrahedra, edges with three equivalent O(5)Bi4 tetrahedra, and edges with three equivalent O(2)Nb3Bi tetrahedra. In the seventh O site, O(7) is bonded in a trigonal planar geometry to three equivalent Bi(1) atoms.