The material structure described by Pb3Nb2O8 crystallizes in the monoclinic P2/m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(3), one O(4), one O(6), one O(7), and one O(8) atom to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Pb(2)O6 octahedra,  a cornercorner with one Pb(3)O6 octahedra, and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-52°. In the second Nb site, Nb(2) is bonded to two equivalent O(5) and four equivalent O(6) atoms to form NbO6 octahedra that share corners with two equivalent Pb(3)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-49°. In the third Nb site, Nb(3) is bonded to two equivalent O(1) and four equivalent O(7) atoms to form NbO6 octahedra that share corners with two equivalent Pb(2)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-48°. There are six inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(5) atom. In the second Pb site, Pb(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form PbO6 octahedra that share corners with two equivalent Nb(3)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. In the third Pb site, Pb(3) is bonded to two equivalent O(5) and four equivalent O(3) atoms to form PbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. In the fourth Pb site, Pb(4) is bonded in a distorted hexagonal planar geometry to two equivalent O(4) and four equivalent O(3) atoms. In the fifth Pb site, Pb(5) is bonded in a 4-coordinate geometry to four equivalent O(2) atoms. In the sixth Pb site, Pb(6) is bonded in a hexagonal planar geometry to two equivalent O(4) and four equivalent O(6) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Nb(3), one Pb(2), and two equivalent Pb(1) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Nb(1), one Pb(1), one Pb(2), and one Pb(5) atom. In the third O site, O(3) is bonded to one Nb(1), one Pb(1), one Pb(3), and one Pb(4) atom to form a mixture of distorted edge and corner-sharing ONbPb3 tetrahedra. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Nb(1), one Pb(4), and one Pb(6) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Nb(2), one Pb(3), and two equivalent Pb(1) atoms. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Nb(1), one Nb(2), and one Pb(6) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to two equivalent Nb(1) atoms. is represented by the CIF file [CIF]
data_Nb2Pb3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   15.344
_cell_length_b   10.844
_cell_length_c   7.652
_cell_angle_alpha   90.000
_cell_angle_beta   60.084
_cell_angle_gamma   44.891
_symmetry_Int_Tables_number   1
_cell_volume   635.874
_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  0.995  0.007  0.005  1.0
  Nb  Nb1  1  0.505  0.993  0.995  1.0
  Nb  Nb2  1  0.505  0.993  0.494  1.0
  Nb  Nb3  1  0.750  0.000  0.500  1.0
  Nb  Nb4  1  0.750  0.500  0.000  1.0
  Nb  Nb5  1  0.995  0.007  0.506  1.0
  Pb  Pb6  1  0.015  0.482  0.993  1.0
  Pb  Pb7  1  0.015  0.482  0.476  1.0
  Pb  Pb8  1  0.250  0.000  0.500  1.0
  Pb  Pb9  1  0.250  0.500  0.000  1.0
  Pb  Pb10  1  0.250  0.500  0.500  1.0
  Pb  Pb11  1  0.250  0.000  0.000  1.0
  Pb  Pb12  1  0.485  0.518  0.007  1.0
  Pb  Pb13  1  0.485  0.518  0.524  1.0
  Pb  Pb14  1  0.750  0.000  0.000  1.0
  O  O15  1  0.987  0.343  0.763  1.0
  O  O16  1  0.302  0.078  0.239  1.0
  O  O17  1  0.293  0.327  0.172  1.0
  O  O18  1  0.302  0.078  0.657  1.0
  O  O19  1  0.506  0.060  0.244  1.0
  O  O20  1  0.207  0.673  0.258  1.0
  O  O21  1  0.293  0.327  0.742  1.0
  O  O22  1  0.994  0.940  0.756  1.0
  O  O23  1  0.198  0.922  0.343  1.0
  O  O24  1  0.207  0.673  0.828  1.0
  O  O25  1  0.198  0.922  0.761  1.0
  O  O26  1  0.515  0.316  0.735  1.0
  O  O27  1  0.513  0.657  0.237  1.0
  O  O28  1  0.824  0.046  0.237  1.0
  O  O29  1  0.824  0.301  0.108  1.0
  O  O30  1  0.824  0.046  0.615  1.0
  O  O31  1  0.004  0.044  0.246  1.0
  O  O32  1  0.676  0.699  0.255  1.0
  O  O33  1  0.824  0.301  0.745  1.0
  O  O34  1  0.496  0.956  0.754  1.0
  O  O35  1  0.676  0.954  0.385  1.0
  O  O36  1  0.676  0.699  0.892  1.0
  O  O37  1  0.676  0.954  0.763  1.0
  O  O38  1  0.985  0.684  0.265  1.0
[/CIF]
.
The material structure described by Pb3Nb2O8 crystallizes in the monoclinic P2/m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(3), one O(4), one O(6), one O(7), and one O(8) atom to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Pb(2)O6 octahedra,  a cornercorner with one Pb(3)O6 octahedra, and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-52°. In the second Nb site, Nb(2) is bonded to two equivalent O(5) and four equivalent O(6) atoms to form NbO6 octahedra that share corners with two equivalent Pb(3)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-49°. In the third Nb site, Nb(3) is bonded to two equivalent O(1) and four equivalent O(7) atoms to form NbO6 octahedra that share corners with two equivalent Pb(2)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-48°. There are six inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(5) atom. In the second Pb site, Pb(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form PbO6 octahedra that share corners with two equivalent Nb(3)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. In the third Pb site, Pb(3) is bonded to two equivalent O(5) and four equivalent O(3) atoms to form PbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra and corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. In the fourth Pb site, Pb(4) is bonded in a distorted hexagonal planar geometry to two equivalent O(4) and four equivalent O(3) atoms. In the fifth Pb site, Pb(5) is bonded in a 4-coordinate geometry to four equivalent O(2) atoms. In the sixth Pb site, Pb(6) is bonded in a hexagonal planar geometry to two equivalent O(4) and four equivalent O(6) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Nb(3), one Pb(2), and two equivalent Pb(1) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Nb(1), one Pb(1), one Pb(2), and one Pb(5) atom. In the third O site, O(3) is bonded to one Nb(1), one Pb(1), one Pb(3), and one Pb(4) atom to form a mixture of distorted edge and corner-sharing ONbPb3 tetrahedra. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Nb(1), one Pb(4), and one Pb(6) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Nb(2), one Pb(3), and two equivalent Pb(1) atoms. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Nb(1), one Nb(2), and one Pb(6) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to two equivalent Nb(1) atoms. is represented by the CIF file [CIF]
data_Nb2Pb3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   15.344
_cell_length_b   10.844
_cell_length_c   7.652
_cell_angle_alpha   90.000
_cell_angle_beta   60.084
_cell_angle_gamma   44.891
_symmetry_Int_Tables_number   1
_cell_volume   635.874
_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  0.995  0.007  0.005  1.0
  Nb  Nb1  1  0.505  0.993  0.995  1.0
  Nb  Nb2  1  0.505  0.993  0.494  1.0
  Nb  Nb3  1  0.750  0.000  0.500  1.0
  Nb  Nb4  1  0.750  0.500  0.000  1.0
  Nb  Nb5  1  0.995  0.007  0.506  1.0
  Pb  Pb6  1  0.015  0.482  0.993  1.0
  Pb  Pb7  1  0.015  0.482  0.476  1.0
  Pb  Pb8  1  0.250  0.000  0.500  1.0
  Pb  Pb9  1  0.250  0.500  0.000  1.0
  Pb  Pb10  1  0.250  0.500  0.500  1.0
  Pb  Pb11  1  0.250  0.000  0.000  1.0
  Pb  Pb12  1  0.485  0.518  0.007  1.0
  Pb  Pb13  1  0.485  0.518  0.524  1.0
  Pb  Pb14  1  0.750  0.000  0.000  1.0
  O  O15  1  0.987  0.343  0.763  1.0
  O  O16  1  0.302  0.078  0.239  1.0
  O  O17  1  0.293  0.327  0.172  1.0
  O  O18  1  0.302  0.078  0.657  1.0
  O  O19  1  0.506  0.060  0.244  1.0
  O  O20  1  0.207  0.673  0.258  1.0
  O  O21  1  0.293  0.327  0.742  1.0
  O  O22  1  0.994  0.940  0.756  1.0
  O  O23  1  0.198  0.922  0.343  1.0
  O  O24  1  0.207  0.673  0.828  1.0
  O  O25  1  0.198  0.922  0.761  1.0
  O  O26  1  0.515  0.316  0.735  1.0
  O  O27  1  0.513  0.657  0.237  1.0
  O  O28  1  0.824  0.046  0.237  1.0
  O  O29  1  0.824  0.301  0.108  1.0
  O  O30  1  0.824  0.046  0.615  1.0
  O  O31  1  0.004  0.044  0.246  1.0
  O  O32  1  0.676  0.699  0.255  1.0
  O  O33  1  0.824  0.301  0.745  1.0
  O  O34  1  0.496  0.956  0.754  1.0
  O  O35  1  0.676  0.954  0.385  1.0
  O  O36  1  0.676  0.699  0.892  1.0
  O  O37  1  0.676  0.954  0.763  1.0
  O  O38  1  0.985  0.684  0.265  1.0
[/CIF]
.