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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca2Ta2O6F by Materials Project

Ca2Ta2O6F crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ca2+ is bonded in a distorted body-centered cubic geometry to six equivalent O2- and two equivalent F1- atoms. All Ca–O bond lengths are 2.52 Å. Both Ca–F bond lengths are 2.25 Å. Ta+4.50+ is bonded to six equivalent O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Ta–O bond lengths are 2.04 Å. O2- is bonded to two equivalent Ca2+ and two equivalent Ta+4.50+ atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent FCa4 tetrahedra, corners with twelve equivalent OCa2Ta2 tetrahedra, an edgeedge with one FCa4 tetrahedra, and edges with four equivalent OCa2Ta2 tetrahedra. F1- is bonded to four equivalent Ca2+ atoms to form FCa4 tetrahedra that share corners with four equivalent FCa4 tetrahedra, corners with twelve equivalent OCa2Ta2 tetrahedra, and edges with six equivalent OCa2Ta2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3Ta4(O6F)2 by Materials Project

Ca3Ta4(O6F)2 crystallizes in the cubic P4_332 space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to six O2- and two equivalent F1- atoms. There are a spread of Ca–O bond distances ranging from 2.48–2.77 Å. Both Ca–F bond lengths are 2.24 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 40–44°. There are a spread of Ta–O bond distances ranging from 1.98–2.01 Å. In the second Ta5+ site, Ta5+ is bonded to six equivalent O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 40°. All Ta–O bond lengths are 1.99 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Ta5+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms. F1- is bonded in a trigonal planar geometry to three equivalent Ca2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3Ta4(O6F)2 by Materials Project

Ca3Ta4(O6F)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ca2+ is bonded to six O2- and two equivalent F1- atoms to form distorted CaO6F2 hexagonal bipyramids that share edges with four equivalent CaO6F2 hexagonal bipyramids and edges with six TaO6 octahedra. There are two shorter (2.62 Å) and four longer (2.66 Å) Ca–O bond lengths. Both Ca–F bond lengths are 2.23 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six equivalent O2- atoms to form TaO6 octahedra that share corners with six equivalent TaO6 octahedra and edges with six equivalent CaO6F2 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 44°. All Ta–O bond lengths are 1.99 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and edges with four equivalent CaO6F2 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 40–44°. There is four shorter (1.99 Å) and two longer (2.00 Å) Ta–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two Ta5+ atoms. F1- is bonded in a trigonal non-coplanar geometry to three equivalent Ca2+ atoms.

36 MATERIALS SCIENCE↗