The crystal structure described by Ta2O5 crystallizes in the monoclinic Cm space group. There are five inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(11), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form distorted TaO7 pentagonal bipyramids that share corners with two equivalent Ta(3)O6 octahedra,  a cornercorner with one Ta(1)O7 pentagonal bipyramid,  a cornercorner with one Ta(2)O7 pentagonal bipyramid,  a cornercorner with one Ta(5)O7 pentagonal bipyramid,  an edgeedge with one Ta(1)O7 pentagonal bipyramid,  an edgeedge with one Ta(2)O7 pentagonal bipyramid, and  an edgeedge with one Ta(5)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 39-52°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(6), two equivalent O(4), and two equivalent O(5) atoms to form distorted TaO7 pentagonal bipyramids that share corners with two equivalent Ta(3)O6 octahedra, corners with two equivalent Ta(1)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O7 pentagonal bipyramids, and edges with two equivalent Ta(5)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 33-45°. In the third Ta site, Ta(3) is bonded to one O(2), one O(6), two equivalent O(3), and two equivalent O(7) atoms to form corner-sharing TaO6 octahedra. In the fourth Ta site, Ta(4) is bonded in a 5-coordinate geometry to one O(10), one O(8), one O(9), and two equivalent O(3) atoms. In the fifth Ta site, Ta(5) is bonded to one O(10), one O(11), one O(9), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing TaO7 pentagonal bipyramids. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to one Ta(2) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Ta(2) and one Ta(3) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Ta(1), one Ta(3), and one Ta(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Ta(1), one Ta(2), and one Ta(5) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ta(1), one Ta(2), and one Ta(5) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ta(2) and one Ta(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ta(1) and one Ta(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Ta(4) and two equivalent Ta(1) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Ta(4) and one Ta(5) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Ta(4) and one Ta(5) atom. In the eleventh O site, O(11) is bonded in a trigonal non-coplanar geometry to one Ta(5) and two equivalent Ta(1) atoms. is represented by the CIF file [CIF]
data_Ta2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.999
_cell_length_b   7.464
_cell_length_c   7.233
_cell_angle_alpha   58.302
_cell_angle_beta   61.072
_cell_angle_gamma   62.042
_symmetry_Int_Tables_number   1
_cell_volume   269.411
_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
  Ta  Ta0  1  0.249  0.985  0.016  1.0
  Ta  Ta1  1  0.239  0.025  0.524  1.0
  Ta  Ta2  1  0.777  0.985  0.016  1.0
  Ta  Ta3  1  0.287  0.472  0.981  1.0
  Ta  Ta4  1  0.719  0.572  0.017  1.0
  Ta  Ta5  1  0.784  0.978  0.482  1.0
  O  O6  1  0.066  0.080  0.817  1.0
  O  O7  1  0.195  0.321  0.316  1.0
  O  O8  1  0.396  0.650  0.048  1.0
  O  O9  1  0.156  0.965  0.334  1.0
  O  O10  1  0.462  0.031  0.671  1.0
  O  O11  1  0.313  0.706  0.695  1.0
  O  O12  1  0.209  0.289  0.931  1.0
  O  O13  1  0.555  0.863  0.053  1.0
  O  O14  1  0.748  0.285  0.246  1.0
  O  O15  1  0.573  0.965  0.335  1.0
  O  O16  1  0.864  0.031  0.671  1.0
  O  O17  1  0.599  0.288  0.931  1.0
  O  O18  1  0.934  0.650  0.048  1.0
  O  O19  1  0.834  0.658  0.700  1.0
  O  O20  1  0.968  0.880  0.211  1.0
[/CIF]
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The crystal structure described by Ta2O5 crystallizes in the monoclinic Cm space group. There are five inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(11), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form distorted TaO7 pentagonal bipyramids that share corners with two equivalent Ta(3)O6 octahedra,  a cornercorner with one Ta(1)O7 pentagonal bipyramid,  a cornercorner with one Ta(2)O7 pentagonal bipyramid,  a cornercorner with one Ta(5)O7 pentagonal bipyramid,  an edgeedge with one Ta(1)O7 pentagonal bipyramid,  an edgeedge with one Ta(2)O7 pentagonal bipyramid, and  an edgeedge with one Ta(5)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 39-52°. In the second Ta site, Ta(2) is bonded to one O(1), one O(2), one O(6), two equivalent O(4), and two equivalent O(5) atoms to form distorted TaO7 pentagonal bipyramids that share corners with two equivalent Ta(3)O6 octahedra, corners with two equivalent Ta(1)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O7 pentagonal bipyramids, and edges with two equivalent Ta(5)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 33-45°. In the third Ta site, Ta(3) is bonded to one O(2), one O(6), two equivalent O(3), and two equivalent O(7) atoms to form corner-sharing TaO6 octahedra. In the fourth Ta site, Ta(4) is bonded in a 5-coordinate geometry to one O(10), one O(8), one O(9), and two equivalent O(3) atoms. In the fifth Ta site, Ta(5) is bonded to one O(10), one O(11), one O(9), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing TaO7 pentagonal bipyramids. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to one Ta(2) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Ta(2) and one Ta(3) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Ta(1), one Ta(3), and one Ta(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Ta(1), one Ta(2), and one Ta(5) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ta(1), one Ta(2), and one Ta(5) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ta(2) and one Ta(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ta(1) and one Ta(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Ta(4) and two equivalent Ta(1) atoms. In the ninth O site, O(9) is bonded in a linear geometry to one Ta(4) and one Ta(5) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Ta(4) and one Ta(5) atom. In the eleventh O site, O(11) is bonded in a trigonal non-coplanar geometry to one Ta(5) and two equivalent Ta(1) atoms. is represented by the CIF file [CIF]
data_Ta2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.999
_cell_length_b   7.464
_cell_length_c   7.233
_cell_angle_alpha   58.302
_cell_angle_beta   61.072
_cell_angle_gamma   62.042
_symmetry_Int_Tables_number   1
_cell_volume   269.411
_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
  Ta  Ta0  1  0.249  0.985  0.016  1.0
  Ta  Ta1  1  0.239  0.025  0.524  1.0
  Ta  Ta2  1  0.777  0.985  0.016  1.0
  Ta  Ta3  1  0.287  0.472  0.981  1.0
  Ta  Ta4  1  0.719  0.572  0.017  1.0
  Ta  Ta5  1  0.784  0.978  0.482  1.0
  O  O6  1  0.066  0.080  0.817  1.0
  O  O7  1  0.195  0.321  0.316  1.0
  O  O8  1  0.396  0.650  0.048  1.0
  O  O9  1  0.156  0.965  0.334  1.0
  O  O10  1  0.462  0.031  0.671  1.0
  O  O11  1  0.313  0.706  0.695  1.0
  O  O12  1  0.209  0.289  0.931  1.0
  O  O13  1  0.555  0.863  0.053  1.0
  O  O14  1  0.748  0.285  0.246  1.0
  O  O15  1  0.573  0.965  0.335  1.0
  O  O16  1  0.864  0.031  0.671  1.0
  O  O17  1  0.599  0.288  0.931  1.0
  O  O18  1  0.934  0.650  0.048  1.0
  O  O19  1  0.834  0.658  0.700  1.0
  O  O20  1  0.968  0.880  0.211  1.0
[/CIF]
.