Materials Data on Li2CaTa2O7 by Materials Project

Abstract

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.