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Ta2O5 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are twenty-two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 4–31°. There are a spread of Ta–O bond distances ranging from 1.95–2.09 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 6–53°. There are a spread of Ta–O bond distances ranging from 1.94–2.09 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 pentagonal pyramids that share corners with two TaO6 octahedra, corners with two equivalent TaO6 pentagonal pyramids, an edgeedge with one TaO6 octahedra, an edgeedge with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 25–26°. There are a spread of Ta–O bond distances ranging from 1.96–2.11 Å. In the fourth Ta5+ site, Ta5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ta–O bond distances ranging from 1.94–2.18 Å. In the fifth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, corners with four TaO6 pentagonal pyramids, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 15°. There are a spread of Ta–O bond distances ranging from 1.90–2.12 Å. In the sixth Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 22–25°. There are a spread of Ta–O bond distances ranging from 1.95–2.11 Å. In the seventh Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 pentagonal pyramids that share corners with two TaO6 octahedra, corners with two equivalent TaO6 pentagonal pyramids, an edgeedge with one TaO6 octahedra, an edgeedge with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 22–28°. There are a spread of Ta–O bond distances ranging from 1.96–2.07 Å. In the eighth Ta5+ site, Ta5+ is bonded to seven O2- atoms to form distorted TaO7 pentagonal bipyramids that share corners with two TaO6 octahedra, corners with two equivalent TaO7 pentagonal bipyramids, and an edgeedge with one TaO6 octahedra. The corner-sharing octahedra tilt angles range from 43–47°. There are a spread of Ta–O bond distances ranging from 1.94–2.45 Å. In the ninth Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 pentagonal pyramids that share corners with two TaO6 octahedra, corners with two equivalent TaO6 pentagonal pyramids, an edgeedge with one TaO6 octahedra, an edgeedge with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 26–27°. There are a spread of Ta–O bond distances ranging from 1.96–2.09 Å. In the tenth Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 octahedra that share corners with five TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, a cornercorner with one TaO6 pentagonal pyramid, and an edgeedge with one TaO6 octahedra. The corner-sharing octahedra tilt angles range from 6–58°. There are a spread of Ta–O bond distances ranging from 1.88–2.15 Å. In the eleventh Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, corners with two TaO6 pentagonal pyramids, an edgeedge with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 10–37°. There are a spread of Ta–O bond distances ranging from 1.93–2.07 Å. In the twelfth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three TaO6 octahedra, corners with two TaO7 pentagonal bipyramids, and an edgeedge with one TaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 13–37°. There are a spread of Ta–O bond distances ranging from 1.93–2.13 Å. In the thirteenth Ta5+ site, Ta5+ is bonded to seven O2- atoms to form distorted TaO7 pentagonal bipyramids that share corners with two TaO6 octahedra, corners with two equivalent TaO7 pentagonal bipyramids, edges with two TaO6 octahedra, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 14–35°. There are a spread of Ta–O bond distances ranging from 1.94–2.42 Å. In the fourteenth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, corners with three TaO6 pentagonal pyramids, an edgeedge with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 8°. There are a spread of Ta–O bond distances ranging from 1.93–2.09 Å. In the fifteenth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 7–41°. There are a spread of Ta–O bond distances ranging from 1.93–2.06 Å. In the sixteenth Ta5+ site, Ta5+ is bonded to seven O2- atoms to form distorted TaO7 pentagonal bipyramids that share corners with two TaO6 octahedra, corners with two equivalent TaO7 pentagonal bipyramids, a cornercorner with one TaO6 pentagonal pyramid, an edgeedge with one TaO6 octahedra, and edges with two TaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 38–46°. There are a spread of Ta–O bond distances ranging from 1.94–2.47 Å. In the seventeenth Ta5+ site, Ta5+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ta–O bond distances ranging from 1.94–2.57 Å. In the eighteenth Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 pentagonal pyramids that share corners with three TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, corners with three TaO6 pentagonal pyramids, and an edgeedge with one TaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 38–66°. There are a spread of Ta–O bond distances ranging from 1.92–2.19 Å. In the nineteenth Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 10–41°. There are a spread of Ta–O bond distances ranging from 1.93–2.09 Å. In the twentieth Ta5+ site, Ta5+ is bonded to seven O2- atoms to form distorted TaO7 pentagonal bipyramids that share corners with three TaO6 octahedra, corners with two equivalent TaO7 pentagonal bipyramids, edges with two TaO6 octahedra, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 7–51°. There are a spread of Ta–O bond distances ranging from 1.94–2.41 Å. In the twenty-first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, corners with two TaO6 pentagonal pyramids, an edgeedge with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 9–38°. There are a spread of Ta–O bond distances ranging from 1.93–2.06 Å. In the twenty-second Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 octahedra that share corners with six TaO6 octahedra, a cornercorner with one TaO7 pentagonal bipyramid, and an edgeedge with one TaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 18–58°. There are a spread of Ta–O bond distances ranging from 1.93–2.16 Å. There are fifty-five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the sixth O2- site, O2- is bonded in a distorted linear geometry to two Ta5+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to three Ta5+ atoms. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to three Ta5+ atoms. In the ninth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the eleventh O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the thirteenth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the fourteenth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the sixteenth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the nineteenth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the twentieth O2- site, O2- is bonded in a distorted T-shaped geometry to three Ta5+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted T-shaped geometry to three Ta5+ atoms. In the twenty-second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the twenty-fifth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the twenty-sixth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the twenty-seventh O2- site, O2- is bonded in a trigonal planar geometry to three Ta5+ atoms. In the twenty-eighth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the twenty-ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the thirtieth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the thirty-first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to three Ta5+ atoms. In the thirty-second O2- site, O2- is bonded in a distorted T-shaped geometry to three Ta5+ atoms. In the thirty-third O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the thirty-fourth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the thirty-fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the thirty-sixth O2- site, O2- is bonded in a 2-coordinate geometry to three Ta5+ atoms. In the thirty-seventh O2- site, O2- is bonded in a trigonal planar geometry to three Ta5+ atoms. In the thirty-eighth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the thirty-ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the fortieth O

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