DOE OSTI2020
Sr20Ta8O39 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twenty inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with three equivalent SrO12 cuboctahedra, a faceface with one SrO6 octahedra, and faces with seven TaO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.64–3.19 Å. In the second Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.54–2.82 Å. In the third Sr2+ site, Sr2+ is bonded to six O2- atoms to form SrO6 octahedra that share a cornercorner with one SrO6 octahedra, corners with three equivalent TaO6 octahedra, corners with three equivalent TaO5 trigonal bipyramids, and a faceface with one SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 13–29°. There are a spread of Sr–O bond distances ranging from 2.38–2.68 Å. In the fourth Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.73 Å. In the fifth Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with three equivalent SrO12 cuboctahedra, a faceface with one SrO6 octahedra, and faces with seven TaO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.66–3.19 Å. In the sixth Sr2+ site, Sr2+ is bonded to six O2- atoms to form distorted SrO6 octahedra that share a cornercorner with one SrO6 octahedra, corners with three equivalent TaO6 octahedra, and corners with three equivalent TaO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 21–29°. There are a spread of Sr–O bond distances ranging from 2.40–2.65 Å. In the seventh Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.57–2.90 Å. In the eighth Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.88 Å. In the ninth Sr2+ site, Sr2+ is bonded to six O2- atoms to form SrO6 pentagonal pyramids that share a cornercorner with one SrO7 hexagonal pyramid, corners with three equivalent TaO6 octahedra, a cornercorner with one SrO6 pentagonal pyramid, corners with three equivalent TaO5 trigonal bipyramids, edges with two SrO7 hexagonal pyramids, and a faceface with one SrO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 20–28°. There are a spread of Sr–O bond distances ranging from 2.42–2.68 Å. In the tenth Sr2+ site, Sr2+ is bonded to seven O2- atoms to form distorted SrO7 hexagonal pyramids that share corners with three equivalent SrO7 hexagonal pyramids, a cornercorner with one SrO6 pentagonal pyramid, edges with two SrO6 pentagonal pyramids, edges with two equivalent TaO5 trigonal bipyramids, a faceface with one TaO6 octahedra, and a faceface with one SrO6 pentagonal pyramid. There are a spread of Sr–O bond distances ranging from 2.51–2.85 Å. In the eleventh Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.56–2.89 Å. In the twelfth Sr2+ site, Sr2+ is bonded to six O2- atoms to form SrO6 pentagonal pyramids that share a cornercorner with one SrO7 hexagonal pyramid, corners with three equivalent TaO6 octahedra, a cornercorner with one SrO6 pentagonal pyramid, corners with three equivalent TaO5 trigonal bipyramids, edges with two SrO7 hexagonal pyramids, and a faceface with one SrO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 14–26°. There are a spread of Sr–O bond distances ranging from 2.41–2.66 Å. In the thirteenth Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–2.82 Å. In the fourteenth Sr2+ site, Sr2+ is bonded to seven O2- atoms to form distorted SrO7 hexagonal pyramids that share corners with three equivalent SrO7 hexagonal pyramids, a cornercorner with one SrO6 pentagonal pyramid, edges with two SrO6 pentagonal pyramids, edges with two equivalent TaO5 trigonal bipyramids, a faceface with one TaO6 octahedra, and a faceface with one SrO6 pentagonal pyramid. There are a spread of Sr–O bond distances ranging from 2.50–2.76 Å. In the fifteenth Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.89 Å. In the sixteenth Sr2+ site, Sr2+ is bonded to six O2- atoms to form distorted SrO6 octahedra that share a cornercorner with one SrO6 octahedra, corners with three equivalent TaO6 octahedra, and corners with three equivalent TaO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 14–29°. There are a spread of Sr–O bond distances ranging from 2.41–2.63 Å. In the seventeenth Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.57–2.86 Å. In the eighteenth Sr2+ site, Sr2+ is bonded to six O2- atoms to form SrO6 octahedra that share a cornercorner with one SrO6 octahedra, corners with three equivalent TaO6 octahedra, corners with three equivalent TaO5 trigonal bipyramids, and a faceface with one SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 12–29°. There are a spread of Sr–O bond distances ranging from 2.38–2.68 Å. In the nineteenth Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–2.86 Å. In the twentieth Sr2+ site, Sr2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.53–3.14 Å. There are eight inequivalent Ta+4.75+ sites. In the first Ta+4.75+ site, Ta+4.75+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent SrO6 octahedra, corners with three equivalent TaO6 octahedra, and faces with four SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 5–16°. There are a spread of Ta–O bond distances ranging from 1.99–2.09 Å. In the second Ta+4.75+ site, Ta+4.75+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with six SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–11°. There are a spread of Ta–O bond distances ranging from 2.05–2.08 Å. In the third Ta+4.75+ site, Ta+4.75+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent SrO6 octahedra, corners with three equivalent TaO6 octahedra, and faces with four SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–18°. There are a spread of Ta–O bond distances ranging from 1.99–2.09 Å. In the fourth Ta+4.75+ site, Ta+4.75+ is bonded to five O2- atoms to form TaO5 trigonal bipyramids that share corners with six SrO6 octahedra. The corner-sharing octahedra tilt angles range from 27–76°. There are a spread of Ta–O bond distances ranging from 1.90–2.01 Å. In the fifth Ta+4.75+ site, Ta+4.75+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent SrO6 octahedra, corners with three equivalent SrO6 pentagonal pyramids, and a faceface with one SrO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 21–24°. There are a spread of Ta–O bond distances ranging from 2.00–2.05 Å. In the sixth Ta+4.75+ site, Ta+4.75+ is bonded to five O2- atoms to form TaO5 trigonal bipyramids that share corners with six SrO6 pentagonal pyramids and edges with four SrO7 hexagonal pyramids. There are a spread of Ta–O bond distances ranging from 1.89–2.01 Å. In the seventh Ta+4.75+ site, Ta+4.75+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent SrO6 octahedra, corners with three equivalent SrO6 pentagonal pyramids, and a faceface with one SrO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 14–25°. There are a spread of Ta–O bond distances ranging from 1.99–2.04 Å. In the eighth Ta+4.75+ site, Ta+4.75+ is bonded to five O2- atoms to form TaO5 trigonal bipyramids that share corners with six SrO6 octahedra. The corner-sharing octahedra tilt angles range from 29–76°. There are a spread of Ta–O bond distances ranging from 1.90–2.00 Å. There are thirty-nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two Ta+4.75+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two Ta+4.75+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two Ta+4.75+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two Ta+4.75+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two Ta+4.75+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two Ta+4.75+ atoms. In the ninth O2- site, O2- is bonded in a distorted see-saw-like geometry to three Sr2+ and one Ta+4.75+ atom. In the tenth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the eleventh O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twelfth O2- site, O2- is bonded in a distorted square pyramidal geometry to four Sr2+ and one Ta+4.75+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Sr2+ and one Ta+4.75+ atom. In the fourteenth O2- site, O2- is bonded in a distorted see-saw-like geometry to three Sr2+ and one Ta+4.75+ atom. In the fifteenth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the sixteenth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the seventeenth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the eighteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Sr2+ and one Ta+4.75+ atom. In the nineteenth O2- site, O2- is bonded in a distorted see-saw-like geometry to three Sr2+ and one Ta+4.75+ atom. In the twentieth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twenty-first O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twenty-second O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twenty-third O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twenty-fourth O2- site, O2- is bonded in a 1-coordinate geometry to three Sr2+ and one Ta+4.75+ atom. In the twenty-fifth O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twenty-sixth O2- site, O2- is bonded in a distorted see-saw-like geometry to three Sr2+ and one Ta+4.75+ atom. In the twenty-seventh O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the twenty-eighth O2- site, O2- is bonded in a 1-coordinate geometry to three Sr2+ and one Ta+4.75+ atom. In the twenty-ninth O2- site, O2- is bonded in a distorted square pyramidal geometry to four Sr2+ and one Ta+4.75+ atom. In the thirtieth O2- site, O2- is bonded in a distorted see-saw-like geometry to three Sr2+ and one Ta+4.75+ atom. In the thirty-first O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Ta+4.75+ atom. In the thirty-second O2- site, O2- is bonded in a 5-coordinate geometry to fo