Pb3Nb2O8 crystallizes in the monoclinic P2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(11), one O(4), one O(5), one O(6), one O(8), and one O(9) atom to form NbO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Pb(3)O6 octahedra,  a cornercorner with one Pb(4)O6 octahedra, and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-51°. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(12), one O(2), one O(3), and one O(5) atom to form NbO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Pb(3)O6 octahedra,  a cornercorner with one Pb(4)O6 octahedra, and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-53°. In the third Nb site, Nb(3) is bonded to two equivalent O(10), two equivalent O(7), and two equivalent O(8) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Pb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-49°. In the fourth Nb site, Nb(4) is bonded to two equivalent O(1), two equivalent O(12), and two equivalent O(9) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Pb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-48°. There are seven inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 4-coordinate geometry to one O(1), one O(4), one O(6), and one O(7) atom. In the second Pb site, Pb(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(7) atom. In the third Pb site, Pb(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form PbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-51°. In the fourth Pb site, Pb(4) is bonded to two equivalent O(3), two equivalent O(6), and two equivalent O(7) atoms to form PbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. In the fifth Pb site, Pb(5) is bonded in a distorted hexagonal planar geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the sixth Pb site, Pb(6) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. In the seventh Pb site, Pb(7) is bonded in a hexagonal planar geometry to two equivalent O(10), two equivalent O(5), and two equivalent O(8) atoms. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Nb(4), one Pb(1), one Pb(2), and one Pb(3) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Nb(2), one Pb(2), one Pb(3), and one Pb(6) atom. In the third O site, O(3) is bonded to one Nb(2), one Pb(2), one Pb(4), and one Pb(5) atom to form a mixture of distorted edge and corner-sharing ONbPb3 tetrahedra. In the fourth O site, O(4) is bonded to one Nb(1), one Pb(1), one Pb(3), and one Pb(6) atom to form distorted edge-sharing ONbPb3 tetrahedra. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(2), one Pb(5), and one Pb(7) atom. In the sixth O site, O(6) is bonded to one Nb(1), one Pb(1), one Pb(4), and one Pb(5) atom to form a mixture of distorted edge and corner-sharing ONbPb3 tetrahedra. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Nb(3), one Pb(1), one Pb(2), and one Pb(4) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(1), one Nb(3), and one Pb(7) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Nb(2), one Nb(3), and one Pb(7) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(4) atom.
Pb3Nb2O8 crystallizes in the monoclinic P2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(11), one O(4), one O(5), one O(6), one O(8), and one O(9) atom to form NbO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Pb(3)O6 octahedra,  a cornercorner with one Pb(4)O6 octahedra, and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-51°. The Nb(1)-O(11) bond length is 2.06 Å. The Nb(1)-O(4) bond length is 2.07 Å. The Nb(1)-O(5) bond length is 1.97 Å. The Nb(1)-O(6) bond length is 2.11 Å. The Nb(1)-O(8) bond length is 1.98 Å. The Nb(1)-O(9) bond length is 1.92 Å. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(12), one O(2), one O(3), and one O(5) atom to form NbO6 octahedra that share  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra,  a cornercorner with one Pb(3)O6 octahedra,  a cornercorner with one Pb(4)O6 octahedra, and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-53°. The Nb(2)-O(10) bond length is 2.04 Å. The Nb(2)-O(11) bond length is 1.90 Å. The Nb(2)-O(12) bond length is 1.94 Å. The Nb(2)-O(2) bond length is 2.02 Å. The Nb(2)-O(3) bond length is 2.09 Å. The Nb(2)-O(5) bond length is 2.14 Å. In the third Nb site, Nb(3) is bonded to two equivalent O(10), two equivalent O(7), and two equivalent O(8) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Pb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-49°. Both Nb(3)-O(10) bond lengths are 1.99 Å. Both Nb(3)-O(7) bond lengths are 1.99 Å. Both Nb(3)-O(8) bond lengths are 2.05 Å. In the fourth Nb site, Nb(4) is bonded to two equivalent O(1), two equivalent O(12), and two equivalent O(9) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Pb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-48°. Both Nb(4)-O(1) bond lengths are 1.99 Å. Both Nb(4)-O(12) bond lengths are 2.03 Å. Both Nb(4)-O(9) bond lengths are 2.03 Å. There are seven inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 4-coordinate geometry to one O(1), one O(4), one O(6), and one O(7) atom. The Pb(1)-O(1) bond length is 2.78 Å. The Pb(1)-O(4) bond length is 2.53 Å. The Pb(1)-O(6) bond length is 2.43 Å. The Pb(1)-O(7) bond length is 2.59 Å. In the second Pb site, Pb(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(7) atom. The Pb(2)-O(1) bond length is 2.67 Å. The Pb(2)-O(2) bond length is 2.53 Å. The Pb(2)-O(3) bond length is 2.52 Å. The Pb(2)-O(7) bond length is 2.68 Å. In the third Pb site, Pb(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form PbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Nb(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-51°. Both Pb(3)-O(1) bond lengths are 2.20 Å. Both Pb(3)-O(2) bond lengths are 2.18 Å. Both Pb(3)-O(4) bond lengths are 2.18 Å. In the fourth Pb site, Pb(4) is bonded to two equivalent O(3), two equivalent O(6), and two equivalent O(7) atoms to form PbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Nb(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. Both Pb(4)-O(3) bond lengths are 2.20 Å. Both Pb(4)-O(6) bond lengths are 2.20 Å. Both Pb(4)-O(7) bond lengths are 2.21 Å. In the fifth Pb site, Pb(5) is bonded in a distorted hexagonal planar geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. Both Pb(5)-O(3) bond lengths are 2.61 Å. Both Pb(5)-O(5) bond lengths are 2.80 Å. Both Pb(5)-O(6) bond lengths are 2.66 Å. In the sixth Pb site, Pb(6) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. Both Pb(6)-O(2) bond lengths are 2.75 Å. Both Pb(6)-O(4) bond lengths are 2.59 Å. In the seventh Pb site, Pb(7) is bonded in a hexagonal planar geometry to two equivalent O(10), two equivalent O(5), and two equivalent O(8) atoms. Both Pb(7)-O(10) bond lengths are 2.73 Å. Both Pb(7)-O(5) bond lengths are 2.73 Å. Both Pb(7)-O(8) bond lengths are 2.79 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Nb(4), one Pb(1), one Pb(2), and one Pb(3) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Nb(2), one Pb(2), one Pb(3), and one Pb(6) atom. In the third O site, O(3) is bonded to one Nb(2), one Pb(2), one Pb(4), and one Pb(5) atom to form a mixture of distorted edge and corner-sharing ONbPb3 tetrahedra. In the fourth O site, O(4) is bonded to one Nb(1), one Pb(1), one Pb(3), and one Pb(6) atom to form distorted edge-sharing ONbPb3 tetrahedra. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Nb(1), one Nb(2), one Pb(5), and one Pb(7) atom. In the sixth O site, O(6) is bonded to one Nb(1), one Pb(1), one Pb(4), and one Pb(5) atom to form a mixture of distorted edge and corner-sharing ONbPb3 tetrahedra. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Nb(3), one Pb(1), one Pb(2), and one Pb(4) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(1), one Nb(3), and one Pb(7) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Nb(2), one Nb(3), and one Pb(7) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Nb(2) and one Nb(4) atom.