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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Li2CaTa2O7 by Materials Project

Li2CaTa2O7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Li–O bond lengths are 2.09 Å. Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with four equivalent CaO12 cuboctahedra, faces with four equivalent CaO12 cuboctahedra, and faces with eight equivalent TaO6 octahedra. There are eight shorter (2.71 Å) and four longer (2.80 Å) Ca–O bond lengths. Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with five equivalent TaO6 octahedra and faces with four equivalent CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–13°. There are a spread of Ta–O bond distances ranging from 1.91–2.08 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded to four equivalent Li1+ and one Ta5+ atom to form a mixture of distorted edge and corner-sharing OLi4Ta trigonal bipyramids. In the third O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ca2+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2CaTa2O7 by Materials Project

Li2CaTa2O7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Li1+ is bonded to five O2- atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent TaO6 octahedra, corners with four equivalent LiO5 trigonal bipyramids, edges with two equivalent TaO6 octahedra, and edges with four equivalent LiO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 60°. There are a spread of Li–O bond distances ranging from 2.01–2.26 Å. Ca2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.89 Å. Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with five equivalent TaO6 octahedra, corners with two equivalent LiO5 trigonal bipyramids, and edges with two equivalent LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–27°. There are a spread of Ta–O bond distances ranging from 1.89–2.10 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Ca2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded to four equivalent Li1+ and one Ta5+ atom to form a mixture of distorted corner and edge-sharing OLi4Ta trigonal bipyramids. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, two equivalent Ca2+, and two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2CaTa2O7 by Materials Project

Li2CaTa2O7 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to five O2- atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent TaO6 octahedra, corners with four equivalent LiO5 trigonal bipyramids, edges with two equivalent TaO6 octahedra, and edges with four LiO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 58°. There are a spread of Li–O bond distances ranging from 1.98–2.22 Å. In the second Li1+ site, Li1+ is bonded to five O2- atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent TaO6 octahedra, corners with four equivalent LiO5 trigonal bipyramids, edges with two equivalent TaO6 octahedra, and edges with four LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 58–59°. There are a spread of Li–O bond distances ranging from 1.99–2.30 Å. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.65 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with five TaO6 octahedra, corners with two equivalent LiO5 trigonal bipyramids, and edges with two equivalent LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 21–31°. There are a spread of Ta–O bond distances ranging from 1.89–2.12 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with five TaO6 octahedra, corners with two equivalent LiO5 trigonal bipyramids, and edges with two equivalent LiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 20–30°. There are a spread of Ta–O bond distances ranging from 1.89–2.11 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Ca2+, and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, one Ca2+, and two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms. In the fifth O2- site, O2- is bonded to two equivalent Ca2+ and two Ta5+ atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent OCa2Ta2 tetrahedra and a cornercorner with one OLi4Ta trigonal bipyramid. In the sixth O2- site, O2- is bonded to four Li1+ and one Ta5+ atom to form distorted OLi4Ta trigonal bipyramids that share a cornercorner with one OCa2Ta2 tetrahedra and corners with four equivalent OLi4Ta trigonal bipyramids. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to four Li1+ and one Ta5+ atom.

36 MATERIALS SCIENCE↗