BaNb4PbBi4O18 crystallizes in the orthorhombic Amm2 space group. Ba(1) is bonded to two equivalent O(1), two equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Nb(1)O6 octahedra, and faces with four equivalent Nb(2)O6 octahedra. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 6-19°. In the second Nb site, Nb(2) is bonded to one O(2), one O(7), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-19°. Pb(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(5) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a distorted pentagonal planar geometry to one O(6) and four equivalent O(4) atoms. In the second Bi site, Bi(2) is bonded in a distorted pentagonal planar geometry to one O(7) and four equivalent O(4) atoms. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Nb(1) and one Bi(1) atom. In the second O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Nb(2) and one Bi(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms. In the fourth O site, O(2) is bonded to two equivalent Ba(1), two equivalent Nb(2), and one Pb(1) atom to form distorted corner-sharing OBa2Nb2Pb square pyramids. In the fifth O site, O(3) is bonded in a distorted linear geometry to one Ba(1), one Nb(1), and one Nb(2) atom. In the sixth O site, O(4) is bonded to two equivalent Bi(1) and two equivalent Bi(2) atoms to form a mixture of corner and edge-sharing OBi4 tetrahedra. In the seventh O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ba(1), one Nb(1), one Nb(2), and one Pb(1) atom.
BaNb4PbBi4O18 crystallizes in the orthorhombic Amm2 space group. Ba(1) is bonded to two equivalent O(1), two equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Nb(1)O6 octahedra, and faces with four equivalent Nb(2)O6 octahedra. There is one shorter (2.66 Å) and one longer (3.02 Å) Ba(1)-O(1) bond length. Both Ba(1)-O(2) bond lengths are 2.83 Å. All Ba(1)-O(3) bond lengths are 2.90 Å. All Ba(1)-O(5) bond lengths are 2.81 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 6-19°. The Nb(1)-O(1) bond length is 2.19 Å. The Nb(1)-O(6) bond length is 1.90 Å. Both Nb(1)-O(3) bond lengths are 2.09 Å. Both Nb(1)-O(5) bond lengths are 1.96 Å. In the second Nb site, Nb(2) is bonded to one O(2), one O(7), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with two equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-19°. The Nb(2)-O(2) bond length is 2.19 Å. The Nb(2)-O(7) bond length is 1.91 Å. Both Nb(2)-O(3) bond lengths are 1.93 Å. Both Nb(2)-O(5) bond lengths are 2.11 Å. Pb(1) is bonded in a 5-coordinate geometry to one O(2) and four equivalent O(5) atoms. The Pb(1)-O(2) bond length is 2.63 Å. All Pb(1)-O(5) bond lengths are 2.59 Å. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a distorted pentagonal planar geometry to one O(6) and four equivalent O(4) atoms. The Bi(1)-O(6) bond length is 2.46 Å. There are two shorter (2.25 Å) and two longer (2.44 Å) Bi(1)-O(4) bond lengths. In the second Bi site, Bi(2) is bonded in a distorted pentagonal planar geometry to one O(7) and four equivalent O(4) atoms. The Bi(2)-O(7) bond length is 2.39 Å. There are two shorter (2.24 Å) and two longer (2.49 Å) Bi(2)-O(4) bond lengths. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Nb(1) and one Bi(1) atom. In the second O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Nb(2) and one Bi(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ba(1) and two equivalent Nb(1) atoms. In the fourth O site, O(2) is bonded to two equivalent Ba(1), two equivalent Nb(2), and one Pb(1) atom to form distorted corner-sharing OBa2Nb2Pb square pyramids. In the fifth O site, O(3) is bonded in a distorted linear geometry to one Ba(1), one Nb(1), and one Nb(2) atom. In the sixth O site, O(4) is bonded to two equivalent Bi(1) and two equivalent Bi(2) atoms to form a mixture of corner and edge-sharing OBi4 tetrahedra. In the seventh O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ba(1), one Nb(1), one Nb(2), and one Pb(1) atom.