The material described by 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. is represented by the CIF card [CIF]
data_Nb2Pb3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.675
_cell_length_b   7.645
_cell_length_c   10.846
_cell_angle_alpha   89.933
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   636.404
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Nb  Nb0  1  0.009  0.242  0.749  1.0
  Nb  Nb1  1  0.509  0.751  0.245  1.0
  Nb  Nb2  1  0.009  0.758  0.251  1.0
  Nb  Nb3  1  0.743  0.000  0.500  1.0
  Nb  Nb4  1  0.252  0.000  0.000  1.0
  Nb  Nb5  1  0.509  0.249  0.755  1.0
  Pb  Pb6  1  0.989  0.272  0.251  1.0
  Pb  Pb7  1  0.505  0.265  0.247  1.0
  Pb  Pb8  1  0.247  0.500  0.000  1.0
  Pb  Pb9  1  0.750  0.500  0.500  1.0
  Pb  Pb10  1  0.251  0.500  0.500  1.0
  Pb  Pb11  1  0.758  0.500  0.000  1.0
  Pb  Pb12  1  0.505  0.735  0.753  1.0
  Pb  Pb13  1  0.989  0.728  0.749  1.0
  Pb  Pb14  1  0.252  0.000  0.500  1.0
  O  O15  1  0.254  0.235  0.078  1.0
  O  O16  1  0.456  0.549  0.132  1.0
  O  O17  1  0.534  0.544  0.370  1.0
  O  O18  1  0.037  0.550  0.130  1.0
  O  O19  1  0.249  0.757  0.315  1.0
  O  O20  1  0.534  0.456  0.630  1.0
  O  O21  1  0.963  0.542  0.368  1.0
  O  O22  1  0.249  0.243  0.685  1.0
  O  O23  1  0.456  0.451  0.868  1.0
  O  O24  1  0.963  0.458  0.632  1.0
  O  O25  1  0.037  0.450  0.870  1.0
  O  O26  1  0.752  0.765  0.580  1.0
  O  O27  1  0.254  0.765  0.922  1.0
  O  O28  1  0.938  0.076  0.618  1.0
  O  O29  1  0.068  0.077  0.876  1.0
  O  O30  1  0.558  0.075  0.617  1.0
  O  O31  1  0.750  0.253  0.797  1.0
  O  O32  1  0.068  0.923  0.124  1.0
  O  O33  1  0.431  0.074  0.873  1.0
  O  O34  1  0.750  0.747  0.203  1.0
  O  O35  1  0.938  0.924  0.382  1.0
  O  O36  1  0.431  0.926  0.127  1.0
  O  O37  1  0.558  0.925  0.383  1.0
  O  O38  1  0.752  0.235  0.420  1.0
[/CIF]
.
The material described by 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. is represented by the CIF card [CIF]
data_Nb2Pb3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.675
_cell_length_b   7.645
_cell_length_c   10.846
_cell_angle_alpha   89.933
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   636.404
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Nb  Nb0  1  0.009  0.242  0.749  1.0
  Nb  Nb1  1  0.509  0.751  0.245  1.0
  Nb  Nb2  1  0.009  0.758  0.251  1.0
  Nb  Nb3  1  0.743  0.000  0.500  1.0
  Nb  Nb4  1  0.252  0.000  0.000  1.0
  Nb  Nb5  1  0.509  0.249  0.755  1.0
  Pb  Pb6  1  0.989  0.272  0.251  1.0
  Pb  Pb7  1  0.505  0.265  0.247  1.0
  Pb  Pb8  1  0.247  0.500  0.000  1.0
  Pb  Pb9  1  0.750  0.500  0.500  1.0
  Pb  Pb10  1  0.251  0.500  0.500  1.0
  Pb  Pb11  1  0.758  0.500  0.000  1.0
  Pb  Pb12  1  0.505  0.735  0.753  1.0
  Pb  Pb13  1  0.989  0.728  0.749  1.0
  Pb  Pb14  1  0.252  0.000  0.500  1.0
  O  O15  1  0.254  0.235  0.078  1.0
  O  O16  1  0.456  0.549  0.132  1.0
  O  O17  1  0.534  0.544  0.370  1.0
  O  O18  1  0.037  0.550  0.130  1.0
  O  O19  1  0.249  0.757  0.315  1.0
  O  O20  1  0.534  0.456  0.630  1.0
  O  O21  1  0.963  0.542  0.368  1.0
  O  O22  1  0.249  0.243  0.685  1.0
  O  O23  1  0.456  0.451  0.868  1.0
  O  O24  1  0.963  0.458  0.632  1.0
  O  O25  1  0.037  0.450  0.870  1.0
  O  O26  1  0.752  0.765  0.580  1.0
  O  O27  1  0.254  0.765  0.922  1.0
  O  O28  1  0.938  0.076  0.618  1.0
  O  O29  1  0.068  0.077  0.876  1.0
  O  O30  1  0.558  0.075  0.617  1.0
  O  O31  1  0.750  0.253  0.797  1.0
  O  O32  1  0.068  0.923  0.124  1.0
  O  O33  1  0.431  0.074  0.873  1.0
  O  O34  1  0.750  0.747  0.203  1.0
  O  O35  1  0.938  0.924  0.382  1.0
  O  O36  1  0.431  0.926  0.127  1.0
  O  O37  1  0.558  0.925  0.383  1.0
  O  O38  1  0.752  0.235  0.420  1.0
[/CIF]
.