Ta2O5 crystallizes in the monoclinic Pm space group. There are four inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(10), one O(5), one O(6), one O(9), and two equivalent O(1) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra,  a cornercorner with one Ta(4)O7 pentagonal bipyramid, and  an edgeedge with one Ta(4)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 2-46°. In the second Ta site, Ta(2) is bonded to one O(6), one O(7), one O(8), one O(9), and two equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra,  a cornercorner with one Ta(4)O7 pentagonal bipyramid, and  an edgeedge with one Ta(4)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 2-46°. In the third Ta site, Ta(3) is bonded in a 7-coordinate geometry to one O(10), one O(5), one O(6), one O(7), one O(8), and two equivalent O(3) atoms. In the fourth Ta site, Ta(4) is bonded to one O(10), one O(5), one O(7), one O(8), one O(9), and two equivalent O(4) atoms to form distorted TaO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra, corners with two equivalent Ta(4)O7 pentagonal bipyramids,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-30°. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Ta(2) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ta(3) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Ta(4) atoms. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ta(1), one Ta(3), and one Ta(4) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Ta(1), one Ta(2), and one Ta(3) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Ta(2), one Ta(3), and one Ta(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ta(2), one Ta(3), and one Ta(4) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Ta(1), one Ta(2), and one Ta(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Ta(1), one Ta(3), and one Ta(4) atom.
Ta2O5 crystallizes in the monoclinic Pm space group. There are four inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(10), one O(5), one O(6), one O(9), and two equivalent O(1) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra,  a cornercorner with one Ta(4)O7 pentagonal bipyramid, and  an edgeedge with one Ta(4)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 2-46°. The Ta(1)-O(10) bond length is 1.98 Å. The Ta(1)-O(5) bond length is 2.03 Å. The Ta(1)-O(6) bond length is 2.01 Å. The Ta(1)-O(9) bond length is 2.01 Å. Both Ta(1)-O(1) bond lengths are 1.94 Å. In the second Ta site, Ta(2) is bonded to one O(6), one O(7), one O(8), one O(9), and two equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra,  a cornercorner with one Ta(4)O7 pentagonal bipyramid, and  an edgeedge with one Ta(4)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 2-46°. The Ta(2)-O(6) bond length is 2.01 Å. The Ta(2)-O(7) bond length is 1.98 Å. The Ta(2)-O(8) bond length is 2.03 Å. The Ta(2)-O(9) bond length is 2.01 Å. Both Ta(2)-O(2) bond lengths are 1.94 Å. In the third Ta site, Ta(3) is bonded in a 7-coordinate geometry to one O(10), one O(5), one O(6), one O(7), one O(8), and two equivalent O(3) atoms. The Ta(3)-O(10) bond length is 2.55 Å. The Ta(3)-O(5) bond length is 1.93 Å. The Ta(3)-O(6) bond length is 2.16 Å. The Ta(3)-O(7) bond length is 2.56 Å. The Ta(3)-O(8) bond length is 1.93 Å. Both Ta(3)-O(3) bond lengths are 1.95 Å. In the fourth Ta site, Ta(4) is bonded to one O(10), one O(5), one O(7), one O(8), one O(9), and two equivalent O(4) atoms to form distorted TaO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra, corners with two equivalent Ta(4)O7 pentagonal bipyramids,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-30°. The Ta(4)-O(10) bond length is 1.95 Å. The Ta(4)-O(5) bond length is 2.51 Å. The Ta(4)-O(7) bond length is 1.94 Å. The Ta(4)-O(8) bond length is 2.50 Å. The Ta(4)-O(9) bond length is 2.14 Å. Both Ta(4)-O(4) bond lengths are 1.95 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Ta(2) atoms. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ta(3) atoms. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Ta(4) atoms. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ta(1), one Ta(3), and one Ta(4) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Ta(1), one Ta(2), and one Ta(3) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Ta(2), one Ta(3), and one Ta(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ta(2), one Ta(3), and one Ta(4) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Ta(1), one Ta(2), and one Ta(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Ta(1), one Ta(3), and one Ta(4) atom.