The material described by PrNb3O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 10-coordinate geometry to one O(12), one O(14), one O(17), one O(2), two equivalent O(1), two equivalent O(11), and two equivalent O(8) atoms. In the second Pr site, Pr(2) is bonded in a 12-coordinate geometry to one O(10), one O(13), one O(16), one O(3), one O(4), two equivalent O(15), two equivalent O(18), and three equivalent O(9) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(12), one O(13), one O(2), one O(3), and one O(5) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 12-26°. In the second Nb site, Nb(2) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(8) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 1-26°. In the third Nb site, Nb(3) is bonded to one O(1), one O(11), one O(14), one O(17), one O(6), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 1-28°. In the fourth Nb site, Nb(4) is bonded to one O(13), one O(15), one O(18), one O(3), one O(6), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 12-30°. In the fifth Nb site, Nb(5) is bonded to one O(15), one O(16), one O(18), one O(4), one O(7), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-30°. In the sixth Nb site, Nb(6) is bonded to one O(10), one O(14), one O(16), one O(17), one O(4), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-28°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Pr(1), one Nb(2), and one Nb(3) atom to form a mixture of distorted corner and edge-sharing OPr2Nb2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Pr(1), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Pr(2), one Nb(1), and one Nb(4) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Pr(2), one Nb(5), and one Nb(6) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(5) and one Nb(6) atom. In the eighth O site, O(8) is bonded to two equivalent Pr(1), one Nb(2), and one Nb(3) atom to form a mixture of distorted corner and edge-sharing OPr2Nb2 trigonal pyramids. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to three equivalent Pr(2), one Nb(4), and one Nb(5) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Pr(2), one Nb(1), and one Nb(6) atom. In the eleventh O site, O(11) is bonded in a linear geometry to two equivalent Pr(1), one Nb(2), and one Nb(3) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Pr(1), one Nb(1), and one Nb(2) atom. In the thirteenth O site, O(13) is bonded in a distorted linear geometry to one Pr(2), one Nb(1), and one Nb(4) atom. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Pr(1), one Nb(3), and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Pr(2), one Nb(4), and one Nb(5) atom. In the sixteenth O site, O(16) is bonded in a distorted linear geometry to one Pr(2), one Nb(5), and one Nb(6) atom. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to one Pr(1), one Nb(3), and one Nb(6) atom. In the eighteenth O site, O(18) is bonded to two equivalent Pr(2), one Nb(4), and one Nb(5) atom to form distorted edge-sharing OPr2Nb2 tetrahedra. is represented by the CIF file [CIF]
data_PrNb3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.611
_cell_length_b   16.847
_cell_length_c   9.761
_cell_angle_alpha   54.893
_cell_angle_beta   90.263
_cell_angle_gamma   90.465
_symmetry_Int_Tables_number   1
_cell_volume   754.883
_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  0.264  0.911  0.000  1.0
  Pr  Pr1  1  0.259  0.250  0.999  1.0
  Pr  Pr2  1  0.736  0.756  1.000  1.0
  Pr  Pr3  1  0.741  0.416  0.001  1.0
  Nb  Nb4  1  0.248  0.999  0.247  1.0
  Nb  Nb5  1  0.249  0.836  0.732  1.0
  Nb  Nb6  1  0.251  0.658  0.264  1.0
  Nb  Nb7  1  0.251  0.507  0.745  1.0
  Nb  Nb8  1  0.251  0.332  0.263  1.0
  Nb  Nb9  1  0.245  0.167  0.744  1.0
  Nb  Nb10  1  0.751  0.830  0.268  1.0
  Nb  Nb11  1  0.752  0.667  0.753  1.0
  Nb  Nb12  1  0.755  0.499  0.256  1.0
  Nb  Nb13  1  0.749  0.334  0.737  1.0
  Nb  Nb14  1  0.749  0.160  0.255  1.0
  Nb  Nb15  1  0.749  0.008  0.736  1.0
  O  O16  1  0.000  0.905  0.786  1.0
  O  O17  1  0.011  0.928  0.203  1.0
  O  O18  1  1.000  0.762  0.214  1.0
  O  O19  1  0.987  0.573  0.765  1.0
  O  O20  1  0.986  0.417  0.233  1.0
  O  O21  1  0.013  0.094  0.235  1.0
  O  O22  1  0.215  0.908  0.497  1.0
  O  O23  1  0.217  0.571  0.500  1.0
  O  O24  1  0.216  0.238  0.503  1.0
  O  O25  1  0.303  0.767  0.000  1.0
  O  O26  1  0.295  0.424  0.999  1.0
  O  O27  1  0.280  0.098  0.002  1.0
  O  O28  1  0.500  0.921  0.736  1.0
  O  O29  1  0.491  0.919  0.233  1.0
  O  O30  1  0.509  0.748  0.767  1.0
  O  O31  1  0.508  0.588  0.727  1.0
  O  O32  1  0.500  0.745  0.264  1.0
  O  O33  1  0.510  0.593  0.231  1.0
  O  O34  1  0.502  0.407  0.777  1.0
  O  O35  1  0.507  0.407  0.270  1.0
  O  O36  1  0.493  0.259  0.730  1.0
  O  O37  1  0.498  0.260  0.223  1.0
  O  O38  1  0.490  0.074  0.769  1.0
  O  O39  1  0.492  0.079  0.273  1.0
  O  O40  1  0.697  0.899  1.000  1.0
  O  O41  1  0.720  0.568  0.998  1.0
  O  O42  1  0.705  0.243  0.001  1.0
  O  O43  1  0.785  0.759  0.503  1.0
  O  O44  1  0.784  0.429  0.497  1.0
  O  O45  1  0.783  0.096  0.500  1.0
  O  O46  1  0.989  0.739  0.797  1.0
  O  O47  1  0.988  0.604  0.202  1.0
  O  O48  1  0.999  0.396  0.810  1.0
  O  O49  1  0.014  0.249  0.767  1.0
  O  O50  1  0.001  0.271  0.190  1.0
  O  O51  1  0.012  0.063  0.798  1.0
[/CIF]
.
The material described by PrNb3O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 10-coordinate geometry to one O(12), one O(14), one O(17), one O(2), two equivalent O(1), two equivalent O(11), and two equivalent O(8) atoms. In the second Pr site, Pr(2) is bonded in a 12-coordinate geometry to one O(10), one O(13), one O(16), one O(3), one O(4), two equivalent O(15), two equivalent O(18), and three equivalent O(9) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(12), one O(13), one O(2), one O(3), and one O(5) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 12-26°. In the second Nb site, Nb(2) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(8) atom to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 1-26°. In the third Nb site, Nb(3) is bonded to one O(1), one O(11), one O(14), one O(17), one O(6), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 1-28°. In the fourth Nb site, Nb(4) is bonded to one O(13), one O(15), one O(18), one O(3), one O(6), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 12-30°. In the fifth Nb site, Nb(5) is bonded to one O(15), one O(16), one O(18), one O(4), one O(7), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-30°. In the sixth Nb site, Nb(6) is bonded to one O(10), one O(14), one O(16), one O(17), one O(4), and one O(7) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 7-28°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Pr(1), one Nb(2), and one Nb(3) atom to form a mixture of distorted corner and edge-sharing OPr2Nb2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Pr(1), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Pr(2), one Nb(1), and one Nb(4) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Pr(2), one Nb(5), and one Nb(6) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Nb(3) and one Nb(4) atom. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(5) and one Nb(6) atom. In the eighth O site, O(8) is bonded to two equivalent Pr(1), one Nb(2), and one Nb(3) atom to form a mixture of distorted corner and edge-sharing OPr2Nb2 trigonal pyramids. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to three equivalent Pr(2), one Nb(4), and one Nb(5) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Pr(2), one Nb(1), and one Nb(6) atom. In the eleventh O site, O(11) is bonded in a linear geometry to two equivalent Pr(1), one Nb(2), and one Nb(3) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Pr(1), one Nb(1), and one Nb(2) atom. In the thirteenth O site, O(13) is bonded in a distorted linear geometry to one Pr(2), one Nb(1), and one Nb(4) atom. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Pr(1), one Nb(3), and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Pr(2), one Nb(4), and one Nb(5) atom. In the sixteenth O site, O(16) is bonded in a distorted linear geometry to one Pr(2), one Nb(5), and one Nb(6) atom. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to one Pr(1), one Nb(3), and one Nb(6) atom. In the eighteenth O site, O(18) is bonded to two equivalent Pr(2), one Nb(4), and one Nb(5) atom to form distorted edge-sharing OPr2Nb2 tetrahedra. is represented by the CIF file [CIF]
data_PrNb3O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.611
_cell_length_b   16.847
_cell_length_c   9.761
_cell_angle_alpha   54.893
_cell_angle_beta   90.263
_cell_angle_gamma   90.465
_symmetry_Int_Tables_number   1
_cell_volume   754.883
_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  0.264  0.911  0.000  1.0
  Pr  Pr1  1  0.259  0.250  0.999  1.0
  Pr  Pr2  1  0.736  0.756  1.000  1.0
  Pr  Pr3  1  0.741  0.416  0.001  1.0
  Nb  Nb4  1  0.248  0.999  0.247  1.0
  Nb  Nb5  1  0.249  0.836  0.732  1.0
  Nb  Nb6  1  0.251  0.658  0.264  1.0
  Nb  Nb7  1  0.251  0.507  0.745  1.0
  Nb  Nb8  1  0.251  0.332  0.263  1.0
  Nb  Nb9  1  0.245  0.167  0.744  1.0
  Nb  Nb10  1  0.751  0.830  0.268  1.0
  Nb  Nb11  1  0.752  0.667  0.753  1.0
  Nb  Nb12  1  0.755  0.499  0.256  1.0
  Nb  Nb13  1  0.749  0.334  0.737  1.0
  Nb  Nb14  1  0.749  0.160  0.255  1.0
  Nb  Nb15  1  0.749  0.008  0.736  1.0
  O  O16  1  0.000  0.905  0.786  1.0
  O  O17  1  0.011  0.928  0.203  1.0
  O  O18  1  1.000  0.762  0.214  1.0
  O  O19  1  0.987  0.573  0.765  1.0
  O  O20  1  0.986  0.417  0.233  1.0
  O  O21  1  0.013  0.094  0.235  1.0
  O  O22  1  0.215  0.908  0.497  1.0
  O  O23  1  0.217  0.571  0.500  1.0
  O  O24  1  0.216  0.238  0.503  1.0
  O  O25  1  0.303  0.767  0.000  1.0
  O  O26  1  0.295  0.424  0.999  1.0
  O  O27  1  0.280  0.098  0.002  1.0
  O  O28  1  0.500  0.921  0.736  1.0
  O  O29  1  0.491  0.919  0.233  1.0
  O  O30  1  0.509  0.748  0.767  1.0
  O  O31  1  0.508  0.588  0.727  1.0
  O  O32  1  0.500  0.745  0.264  1.0
  O  O33  1  0.510  0.593  0.231  1.0
  O  O34  1  0.502  0.407  0.777  1.0
  O  O35  1  0.507  0.407  0.270  1.0
  O  O36  1  0.493  0.259  0.730  1.0
  O  O37  1  0.498  0.260  0.223  1.0
  O  O38  1  0.490  0.074  0.769  1.0
  O  O39  1  0.492  0.079  0.273  1.0
  O  O40  1  0.697  0.899  1.000  1.0
  O  O41  1  0.720  0.568  0.998  1.0
  O  O42  1  0.705  0.243  0.001  1.0
  O  O43  1  0.785  0.759  0.503  1.0
  O  O44  1  0.784  0.429  0.497  1.0
  O  O45  1  0.783  0.096  0.500  1.0
  O  O46  1  0.989  0.739  0.797  1.0
  O  O47  1  0.988  0.604  0.202  1.0
  O  O48  1  0.999  0.396  0.810  1.0
  O  O49  1  0.014  0.249  0.767  1.0
  O  O50  1  0.001  0.271  0.190  1.0
  O  O51  1  0.012  0.063  0.798  1.0
[/CIF]
.