Nb8Pb6O25 crystallizes in the monoclinic C2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(13), one O(15), one O(2), one O(3), one O(5), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 31-49°. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(2), one O(4), one O(5), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 29-52°. In the third Nb site, Nb(3) is bonded to one O(1), one O(10), one O(12), one O(15), one O(6), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 23-49°. In the fourth Nb site, Nb(4) is bonded to one O(12), one O(13), one O(14), one O(4), one O(6), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 29-47°. There are three inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 4-coordinate geometry to one O(15), one O(5), one O(7), and one O(9) atom. In the second Pb site, Pb(2) is bonded in a 7-coordinate geometry to one O(10), one O(11), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. In the third Pb site, Pb(3) is bonded in a 5-coordinate geometry to one O(12), one O(13), one O(14), one O(2), and one O(6) atom. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Nb(3) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Nb(1), one Nb(2), and one Pb(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Nb(2), one Nb(4), and one Pb(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(2), one Pb(1), and one Pb(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Nb(3), one Nb(4), and one Pb(3) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Nb(3), one Nb(4), one Pb(1), and one Pb(2) atom. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(2), and one Pb(2) atom. In the ninth O site, O(9) is bonded in a tetrahedral geometry to two equivalent Pb(1) and two equivalent Pb(2) atoms. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Nb(2), one Nb(3), and one Pb(2) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to two equivalent Nb(2) and two equivalent Pb(2) atoms. In the twelfth O site, O(12) is bonded in a distorted bent 150 degrees geometry to one Nb(3), one Nb(4), and one Pb(3) atom. In the thirteenth O site, O(13) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(4), and one Pb(3) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to two equivalent Nb(4) and two equivalent Pb(3) atoms. In the fifteenth O site, O(15) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1), one Nb(3), and one Pb(1) atom.
Nb8Pb6O25 crystallizes in the monoclinic C2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(13), one O(15), one O(2), one O(3), one O(5), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 31-49°. The Nb(1)-O(13) bond length is 1.92 Å. The Nb(1)-O(15) bond length is 2.00 Å. The Nb(1)-O(2) bond length is 2.09 Å. The Nb(1)-O(3) bond length is 1.99 Å. The Nb(1)-O(5) bond length is 2.14 Å. The Nb(1)-O(8) bond length is 1.94 Å. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(2), one O(4), one O(5), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 29-52°. The Nb(2)-O(10) bond length is 2.06 Å. The Nb(2)-O(11) bond length is 2.03 Å. The Nb(2)-O(2) bond length is 1.89 Å. The Nb(2)-O(4) bond length is 1.98 Å. The Nb(2)-O(5) bond length is 1.97 Å. The Nb(2)-O(8) bond length is 2.14 Å. In the third Nb site, Nb(3) is bonded to one O(1), one O(10), one O(12), one O(15), one O(6), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 23-49°. The Nb(3)-O(1) bond length is 1.94 Å. The Nb(3)-O(10) bond length is 1.93 Å. The Nb(3)-O(12) bond length is 1.91 Å. The Nb(3)-O(15) bond length is 2.03 Å. The Nb(3)-O(6) bond length is 2.10 Å. The Nb(3)-O(7) bond length is 2.17 Å. In the fourth Nb site, Nb(4) is bonded to one O(12), one O(13), one O(14), one O(4), one O(6), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 29-47°. The Nb(4)-O(12) bond length is 2.06 Å. The Nb(4)-O(13) bond length is 2.16 Å. The Nb(4)-O(14) bond length is 2.02 Å. The Nb(4)-O(4) bond length is 1.96 Å. The Nb(4)-O(6) bond length is 1.88 Å. The Nb(4)-O(7) bond length is 1.98 Å. There are three inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 4-coordinate geometry to one O(15), one O(5), one O(7), and one O(9) atom. The Pb(1)-O(15) bond length is 2.44 Å. The Pb(1)-O(5) bond length is 2.60 Å. The Pb(1)-O(7) bond length is 2.54 Å. The Pb(1)-O(9) bond length is 2.38 Å. In the second Pb site, Pb(2) is bonded in a 7-coordinate geometry to one O(10), one O(11), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. The Pb(2)-O(10) bond length is 2.62 Å. The Pb(2)-O(11) bond length is 2.64 Å. The Pb(2)-O(4) bond length is 2.85 Å. The Pb(2)-O(5) bond length is 2.77 Å. The Pb(2)-O(7) bond length is 2.69 Å. The Pb(2)-O(8) bond length is 2.66 Å. The Pb(2)-O(9) bond length is 2.32 Å. In the third Pb site, Pb(3) is bonded in a 5-coordinate geometry to one O(12), one O(13), one O(14), one O(2), and one O(6) atom. The Pb(3)-O(12) bond length is 2.66 Å. The Pb(3)-O(13) bond length is 2.65 Å. The Pb(3)-O(14) bond length is 2.58 Å. The Pb(3)-O(2) bond length is 2.81 Å. The Pb(3)-O(6) bond length is 2.79 Å. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Nb(3) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Nb(1), one Nb(2), and one Pb(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Nb(2), one Nb(4), and one Pb(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(2), one Pb(1), and one Pb(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Nb(3), one Nb(4), and one Pb(3) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Nb(3), one Nb(4), one Pb(1), and one Pb(2) atom. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(2), and one Pb(2) atom. In the ninth O site, O(9) is bonded in a tetrahedral geometry to two equivalent Pb(1) and two equivalent Pb(2) atoms. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Nb(2), one Nb(3), and one Pb(2) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to two equivalent Nb(2) and two equivalent Pb(2) atoms. In the twelfth O site, O(12) is bonded in a distorted bent 150 degrees geometry to one Nb(3), one Nb(4), and one Pb(3) atom. In the thirteenth O site, O(13) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(4), and one Pb(3) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to two equivalent Nb(4) and two equivalent Pb(3) atoms. In the fifteenth O site, O(15) is bonded in a distorted trigonal non-coplanar geometry to one Nb(1), one Nb(3), and one Pb(1) atom.