The material described by PrNb3O9 crystallizes in the monoclinic P2_1/c space group. Pr(1) is bonded in a 8-coordinate geometry to one O(1), one O(4), one O(5), one O(7), two equivalent O(2), and two equivalent O(3) atoms. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(5), one O(6), one O(9), and two equivalent O(8) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 32-52°. In the second Nb site, Nb(2) is bonded to one O(1), one O(4), one O(7), one O(9), and two equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 27-46°. In the third Nb site, Nb(3) is bonded to one O(4), one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 27-52°. There are nine inequivalent O sites. In the first O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to one Pr(1), one Nb(1), and one Nb(2) atom. In the third O site, O(2) is bonded to two equivalent Pr(1) and two equivalent Nb(3) atoms to form a mixture of distorted corner and edge-sharing OPr2Nb2 tetrahedra. In the fourth O site, O(3) is bonded to two equivalent Pr(1) and two equivalent Nb(2) atoms to form a mixture of distorted corner and edge-sharing OPr2Nb2 tetrahedra. In the fifth O site, O(4) is bonded in a 3-coordinate geometry to one Pr(1), one Nb(2), and one Nb(3) atom. In the sixth O site, O(5) is bonded in a distorted trigonal planar geometry to one Pr(1), one Nb(1), and one Nb(3) atom. In the seventh O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(3) atom. In the eighth O site, O(7) is bonded in a 3-coordinate geometry to one Pr(1), one Nb(2), and one Nb(3) atom. In the ninth 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_PrNb3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.738
_cell_length_b   5.444
_cell_length_c   16.665
_cell_angle_alpha   87.969
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   701.621
_cell_formula_units_Z   4
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
  Pr  Pr0  1  0.250  0.967  0.468  1.0
  Pr  Pr1  1  0.750  0.033  0.032  1.0
  Pr  Pr2  1  0.250  0.967  0.968  1.0
  Pr  Pr3  1  0.750  0.033  0.532  1.0
  Nb  Nb4  1  0.470  0.992  0.249  1.0
  Nb  Nb5  1  0.030  0.992  0.749  1.0
  Nb  Nb6  1  0.483  0.528  0.600  1.0
  Nb  Nb7  1  0.001  0.480  0.400  1.0
  Nb  Nb8  1  0.499  0.480  0.900  1.0
  Nb  Nb9  1  0.501  0.520  0.100  1.0
  Nb  Nb10  1  0.530  0.008  0.751  1.0
  Nb  Nb11  1  0.017  0.528  0.100  1.0
  Nb  Nb12  1  0.970  0.008  0.251  1.0
  Nb  Nb13  1  0.999  0.520  0.600  1.0
  Nb  Nb14  1  0.983  0.472  0.900  1.0
  Nb  Nb15  1  0.517  0.472  0.400  1.0
  O  O16  1  0.439  0.154  0.356  1.0
  O  O17  1  0.037  0.264  0.517  1.0
  O  O18  1  0.964  0.736  0.983  1.0
  O  O19  1  0.561  0.846  0.644  1.0
  O  O20  1  0.061  0.154  0.856  1.0
  O  O21  1  0.249  0.648  0.581  1.0
  O  O22  1  0.946  0.850  0.644  1.0
  O  O23  1  0.554  0.680  0.810  1.0
  O  O24  1  0.749  0.439  0.095  1.0
  O  O25  1  0.249  0.561  0.405  1.0
  O  O26  1  0.464  0.264  0.517  1.0
  O  O27  1  0.245  0.903  0.241  1.0
  O  O28  1  0.751  0.352  0.419  1.0
  O  O29  1  0.251  0.561  0.905  1.0
  O  O30  1  0.749  0.352  0.919  1.0
  O  O31  1  0.554  0.850  0.144  1.0
  O  O32  1  0.946  0.680  0.310  1.0
  O  O33  1  0.536  0.736  0.483  1.0
  O  O34  1  0.446  0.320  0.190  1.0
  O  O35  1  0.036  0.264  0.017  1.0
  O  O36  1  0.054  0.150  0.356  1.0
  O  O37  1  0.463  0.264  0.017  1.0
  O  O38  1  0.537  0.736  0.983  1.0
  O  O39  1  0.049  0.317  0.189  1.0
  O  O40  1  0.251  0.648  0.081  1.0
  O  O41  1  0.446  0.150  0.856  1.0
  O  O42  1  0.745  0.097  0.259  1.0
  O  O43  1  0.951  0.683  0.811  1.0
  O  O44  1  0.054  0.320  0.690  1.0
  O  O45  1  0.755  0.097  0.759  1.0
  O  O46  1  0.451  0.317  0.689  1.0
  O  O47  1  0.549  0.683  0.311  1.0
  O  O48  1  0.255  0.903  0.741  1.0
  O  O49  1  0.939  0.846  0.144  1.0
  O  O50  1  0.751  0.439  0.595  1.0
  O  O51  1  0.963  0.736  0.483  1.0
[/CIF]
.
The material described by PrNb3O9 crystallizes in the monoclinic P2_1/c space group. Pr(1) is bonded in a 8-coordinate geometry to one O(1), one O(4), one O(5), one O(7), two equivalent O(2), and two equivalent O(3) atoms. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(5), one O(6), one O(9), and two equivalent O(8) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 32-52°. In the second Nb site, Nb(2) is bonded to one O(1), one O(4), one O(7), one O(9), and two equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 27-46°. In the third Nb site, Nb(3) is bonded to one O(4), one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 27-52°. There are nine inequivalent O sites. In the first O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to one Pr(1), one Nb(1), and one Nb(2) atom. In the third O site, O(2) is bonded to two equivalent Pr(1) and two equivalent Nb(3) atoms to form a mixture of distorted corner and edge-sharing OPr2Nb2 tetrahedra. In the fourth O site, O(3) is bonded to two equivalent Pr(1) and two equivalent Nb(2) atoms to form a mixture of distorted corner and edge-sharing OPr2Nb2 tetrahedra. In the fifth O site, O(4) is bonded in a 3-coordinate geometry to one Pr(1), one Nb(2), and one Nb(3) atom. In the sixth O site, O(5) is bonded in a distorted trigonal planar geometry to one Pr(1), one Nb(1), and one Nb(3) atom. In the seventh O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(3) atom. In the eighth O site, O(7) is bonded in a 3-coordinate geometry to one Pr(1), one Nb(2), and one Nb(3) atom. In the ninth 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_PrNb3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.738
_cell_length_b   5.444
_cell_length_c   16.665
_cell_angle_alpha   87.969
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   701.621
_cell_formula_units_Z   4
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
  Pr  Pr0  1  0.250  0.967  0.468  1.0
  Pr  Pr1  1  0.750  0.033  0.032  1.0
  Pr  Pr2  1  0.250  0.967  0.968  1.0
  Pr  Pr3  1  0.750  0.033  0.532  1.0
  Nb  Nb4  1  0.470  0.992  0.249  1.0
  Nb  Nb5  1  0.030  0.992  0.749  1.0
  Nb  Nb6  1  0.483  0.528  0.600  1.0
  Nb  Nb7  1  0.001  0.480  0.400  1.0
  Nb  Nb8  1  0.499  0.480  0.900  1.0
  Nb  Nb9  1  0.501  0.520  0.100  1.0
  Nb  Nb10  1  0.530  0.008  0.751  1.0
  Nb  Nb11  1  0.017  0.528  0.100  1.0
  Nb  Nb12  1  0.970  0.008  0.251  1.0
  Nb  Nb13  1  0.999  0.520  0.600  1.0
  Nb  Nb14  1  0.983  0.472  0.900  1.0
  Nb  Nb15  1  0.517  0.472  0.400  1.0
  O  O16  1  0.439  0.154  0.356  1.0
  O  O17  1  0.037  0.264  0.517  1.0
  O  O18  1  0.964  0.736  0.983  1.0
  O  O19  1  0.561  0.846  0.644  1.0
  O  O20  1  0.061  0.154  0.856  1.0
  O  O21  1  0.249  0.648  0.581  1.0
  O  O22  1  0.946  0.850  0.644  1.0
  O  O23  1  0.554  0.680  0.810  1.0
  O  O24  1  0.749  0.439  0.095  1.0
  O  O25  1  0.249  0.561  0.405  1.0
  O  O26  1  0.464  0.264  0.517  1.0
  O  O27  1  0.245  0.903  0.241  1.0
  O  O28  1  0.751  0.352  0.419  1.0
  O  O29  1  0.251  0.561  0.905  1.0
  O  O30  1  0.749  0.352  0.919  1.0
  O  O31  1  0.554  0.850  0.144  1.0
  O  O32  1  0.946  0.680  0.310  1.0
  O  O33  1  0.536  0.736  0.483  1.0
  O  O34  1  0.446  0.320  0.190  1.0
  O  O35  1  0.036  0.264  0.017  1.0
  O  O36  1  0.054  0.150  0.356  1.0
  O  O37  1  0.463  0.264  0.017  1.0
  O  O38  1  0.537  0.736  0.983  1.0
  O  O39  1  0.049  0.317  0.189  1.0
  O  O40  1  0.251  0.648  0.081  1.0
  O  O41  1  0.446  0.150  0.856  1.0
  O  O42  1  0.745  0.097  0.259  1.0
  O  O43  1  0.951  0.683  0.811  1.0
  O  O44  1  0.054  0.320  0.690  1.0
  O  O45  1  0.755  0.097  0.759  1.0
  O  O46  1  0.451  0.317  0.689  1.0
  O  O47  1  0.549  0.683  0.311  1.0
  O  O48  1  0.255  0.903  0.741  1.0
  O  O49  1  0.939  0.846  0.144  1.0
  O  O50  1  0.751  0.439  0.595  1.0
  O  O51  1  0.963  0.736  0.483  1.0
[/CIF]
.