Materials Data on K2SrTa2O7 by Materials Project
K2SrTa2O7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. K1+ is bonded in a 5-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.78–3.08 Å. Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent TaO6 octahedra. There are eight shorter (2.79 Å) and four longer (2.84 Å) Sr–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 SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Ta–O bond distances ranging from 1.87–2.12 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded to five equivalent K1+ and one Ta5+ atom to form a mixture of distorted edge and corner-sharing OK5Ta octahedra. The corner-sharing octahedral tilt angles are 11°. In the third O2- site, O2- is bonded in a distorted linear geometry to two equivalent K1+, two equivalent Sr2+, and two equivalent Ta5+ atoms.