The crystal structure described by Ta10O9 crystallizes in the monoclinic Cm space group. There are ten inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 4-coordinate geometry to one O(4), one O(9), and two equivalent O(7) atoms. In the second Ta site, Ta(2) is bonded in a 4-coordinate geometry to one O(1), one O(7), and two equivalent O(9) atoms. In the third Ta site, Ta(3) is bonded to one O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted TaO5 trigonal bipyramids that share corners with two equivalent Ta(8)O5 square pyramids, corners with two equivalent Ta(4)O4 trigonal pyramids,  an edgeedge with one Ta(8)O5 square pyramid, edges with two equivalent Ta(3)O5 trigonal bipyramids, and edges with two equivalent Ta(4)O4 trigonal pyramids. In the fourth Ta site, Ta(4) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form distorted TaO4 trigonal pyramids that share corners with two equivalent Ta(8)O5 square pyramids, corners with two equivalent Ta(3)O5 trigonal bipyramids, corners with two equivalent Ta(4)O4 trigonal pyramids, and edges with two equivalent Ta(3)O5 trigonal bipyramids. In the fifth Ta site, Ta(5) is bonded in a distorted single-bond geometry to one O(2), one O(3), and two equivalent O(6) atoms. In the sixth Ta site, Ta(6) is bonded to one O(2), one O(8), two equivalent O(5), and two equivalent O(6) atoms to form distorted TaO6 octahedra that share corners with three equivalent Ta(7)O6 octahedra,  an edgeedge with one Ta(7)O6 octahedra, edges with two equivalent Ta(10)O6 octahedra, edges with two equivalent Ta(6)O6 octahedra, edges with four equivalent Ta(9)O6 octahedra, and edges with two equivalent Ta(8)O5 square pyramids. The corner-sharing octahedral tilt angles range from 0-1°. In the seventh Ta site, Ta(7) is bonded to one O(7), one O(8), two equivalent O(5), and two equivalent O(9) atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the eighth Ta site, Ta(8) is bonded to one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted TaO5 square pyramids that share corners with three equivalent Ta(9)O6 octahedra, corners with two equivalent Ta(3)O5 trigonal bipyramids, corners with two equivalent Ta(4)O4 trigonal pyramids,  an edgeedge with one Ta(9)O6 octahedra, edges with two equivalent Ta(6)O6 octahedra, edges with two equivalent Ta(8)O5 square pyramids, and  an edgeedge with one Ta(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 0-2°. In the ninth Ta site, Ta(9) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form distorted TaO6 octahedra that share corners with three equivalent Ta(10)O6 octahedra, corners with three equivalent Ta(8)O5 square pyramids,  an edgeedge with one Ta(10)O6 octahedra, edges with two equivalent Ta(7)O6 octahedra, edges with two equivalent Ta(9)O6 octahedra, edges with four equivalent Ta(6)O6 octahedra, and  an edgeedge with one Ta(8)O5 square pyramid. The corner-sharing octahedral tilt angles range from 1-4°. In the tenth Ta site, Ta(10) is bonded to one O(5), one O(9), two equivalent O(7), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ta(2), one Ta(3), and two equivalent Ta(4) atoms. In the second O site, O(2) is bonded to one Ta(5), one Ta(6), two equivalent Ta(8), and two equivalent Ta(9) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. In the third O site, O(3) is bonded to one Ta(4), one Ta(5), two equivalent Ta(3), and two equivalent Ta(8) atoms to form a mixture of corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 3-14°. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ta(1), one Ta(4), and two equivalent Ta(3) atoms. In the fifth O site, O(5) is bonded to one Ta(10), one Ta(9), two equivalent Ta(6), and two equivalent Ta(7) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Ta(8), one Ta(9), two equivalent Ta(5), and two equivalent Ta(6) atoms. In the seventh O site, O(7) is bonded to one Ta(2), one Ta(7), two equivalent Ta(1), and two equivalent Ta(10) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the eighth O site, O(8) is bonded to one Ta(6), one Ta(7), two equivalent Ta(10), and two equivalent Ta(9) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the ninth O site, O(9) is bonded to one Ta(1), one Ta(10), two equivalent Ta(2), and two equivalent Ta(7) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta10O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   16.161
_cell_length_b   16.161
_cell_length_c   5.231
_cell_angle_alpha   86.436
_cell_angle_beta   86.436
_cell_angle_gamma   9.759
_symmetry_Int_Tables_number   1
_cell_volume   231.153
_cell_formula_units_Z   1
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
  Ta  Ta0  1  0.004  0.004  0.012  1.0
  Ta  Ta1  1  0.504  0.504  0.510  1.0
  Ta  Ta2  1  0.609  0.609  0.785  1.0
  Ta  Ta3  1  0.117  0.117  0.297  1.0
  Ta  Ta4  1  0.190  0.190  0.608  1.0
  Ta  Ta5  1  0.301  0.301  0.901  1.0
  Ta  Ta6  1  0.403  0.403  0.193  1.0
  Ta  Ta7  1  0.703  0.703  0.112  1.0
  Ta  Ta8  1  0.801  0.801  0.405  1.0
  Ta  Ta9  1  0.902  0.902  0.697  1.0
  O  O10  1  0.571  0.571  0.485  1.0
  O  O11  1  0.251  0.251  0.251  1.0
  O  O12  1  0.154  0.154  0.948  1.0
  O  O13  1  0.069  0.069  0.989  1.0
  O  O14  1  0.853  0.853  0.045  1.0
  O  O15  1  0.757  0.757  0.726  1.0
  O  O16  1  0.452  0.452  0.851  1.0
  O  O17  1  0.350  0.350  0.562  1.0
  O  O18  1  0.951  0.951  0.351  1.0
[/CIF]
.
The crystal structure described by Ta10O9 crystallizes in the monoclinic Cm space group. There are ten inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 4-coordinate geometry to one O(4), one O(9), and two equivalent O(7) atoms. In the second Ta site, Ta(2) is bonded in a 4-coordinate geometry to one O(1), one O(7), and two equivalent O(9) atoms. In the third Ta site, Ta(3) is bonded to one O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted TaO5 trigonal bipyramids that share corners with two equivalent Ta(8)O5 square pyramids, corners with two equivalent Ta(4)O4 trigonal pyramids,  an edgeedge with one Ta(8)O5 square pyramid, edges with two equivalent Ta(3)O5 trigonal bipyramids, and edges with two equivalent Ta(4)O4 trigonal pyramids. In the fourth Ta site, Ta(4) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form distorted TaO4 trigonal pyramids that share corners with two equivalent Ta(8)O5 square pyramids, corners with two equivalent Ta(3)O5 trigonal bipyramids, corners with two equivalent Ta(4)O4 trigonal pyramids, and edges with two equivalent Ta(3)O5 trigonal bipyramids. In the fifth Ta site, Ta(5) is bonded in a distorted single-bond geometry to one O(2), one O(3), and two equivalent O(6) atoms. In the sixth Ta site, Ta(6) is bonded to one O(2), one O(8), two equivalent O(5), and two equivalent O(6) atoms to form distorted TaO6 octahedra that share corners with three equivalent Ta(7)O6 octahedra,  an edgeedge with one Ta(7)O6 octahedra, edges with two equivalent Ta(10)O6 octahedra, edges with two equivalent Ta(6)O6 octahedra, edges with four equivalent Ta(9)O6 octahedra, and edges with two equivalent Ta(8)O5 square pyramids. The corner-sharing octahedral tilt angles range from 0-1°. In the seventh Ta site, Ta(7) is bonded to one O(7), one O(8), two equivalent O(5), and two equivalent O(9) atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the eighth Ta site, Ta(8) is bonded to one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted TaO5 square pyramids that share corners with three equivalent Ta(9)O6 octahedra, corners with two equivalent Ta(3)O5 trigonal bipyramids, corners with two equivalent Ta(4)O4 trigonal pyramids,  an edgeedge with one Ta(9)O6 octahedra, edges with two equivalent Ta(6)O6 octahedra, edges with two equivalent Ta(8)O5 square pyramids, and  an edgeedge with one Ta(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 0-2°. In the ninth Ta site, Ta(9) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form distorted TaO6 octahedra that share corners with three equivalent Ta(10)O6 octahedra, corners with three equivalent Ta(8)O5 square pyramids,  an edgeedge with one Ta(10)O6 octahedra, edges with two equivalent Ta(7)O6 octahedra, edges with two equivalent Ta(9)O6 octahedra, edges with four equivalent Ta(6)O6 octahedra, and  an edgeedge with one Ta(8)O5 square pyramid. The corner-sharing octahedral tilt angles range from 1-4°. In the tenth Ta site, Ta(10) is bonded to one O(5), one O(9), two equivalent O(7), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ta(2), one Ta(3), and two equivalent Ta(4) atoms. In the second O site, O(2) is bonded to one Ta(5), one Ta(6), two equivalent Ta(8), and two equivalent Ta(9) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. In the third O site, O(3) is bonded to one Ta(4), one Ta(5), two equivalent Ta(3), and two equivalent Ta(8) atoms to form a mixture of corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 3-14°. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ta(1), one Ta(4), and two equivalent Ta(3) atoms. In the fifth O site, O(5) is bonded to one Ta(10), one Ta(9), two equivalent Ta(6), and two equivalent Ta(7) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Ta(8), one Ta(9), two equivalent Ta(5), and two equivalent Ta(6) atoms. In the seventh O site, O(7) is bonded to one Ta(2), one Ta(7), two equivalent Ta(1), and two equivalent Ta(10) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the eighth O site, O(8) is bonded to one Ta(6), one Ta(7), two equivalent Ta(10), and two equivalent Ta(9) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the ninth O site, O(9) is bonded to one Ta(1), one Ta(10), two equivalent Ta(2), and two equivalent Ta(7) atoms to form a mixture of distorted corner and edge-sharing OTa6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ta10O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   16.161
_cell_length_b   16.161
_cell_length_c   5.231
_cell_angle_alpha   86.436
_cell_angle_beta   86.436
_cell_angle_gamma   9.759
_symmetry_Int_Tables_number   1
_cell_volume   231.153
_cell_formula_units_Z   1
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
  Ta  Ta0  1  0.004  0.004  0.012  1.0
  Ta  Ta1  1  0.504  0.504  0.510  1.0
  Ta  Ta2  1  0.609  0.609  0.785  1.0
  Ta  Ta3  1  0.117  0.117  0.297  1.0
  Ta  Ta4  1  0.190  0.190  0.608  1.0
  Ta  Ta5  1  0.301  0.301  0.901  1.0
  Ta  Ta6  1  0.403  0.403  0.193  1.0
  Ta  Ta7  1  0.703  0.703  0.112  1.0
  Ta  Ta8  1  0.801  0.801  0.405  1.0
  Ta  Ta9  1  0.902  0.902  0.697  1.0
  O  O10  1  0.571  0.571  0.485  1.0
  O  O11  1  0.251  0.251  0.251  1.0
  O  O12  1  0.154  0.154  0.948  1.0
  O  O13  1  0.069  0.069  0.989  1.0
  O  O14  1  0.853  0.853  0.045  1.0
  O  O15  1  0.757  0.757  0.726  1.0
  O  O16  1  0.452  0.452  0.851  1.0
  O  O17  1  0.350  0.350  0.562  1.0
  O  O18  1  0.951  0.951  0.351  1.0
[/CIF]
.