Materials Data on Sr2Ta2O7 by Materials Project

Abstract

Sr2Ta2O7 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight TaO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.65–2.92 Å. In the second Sr2+ site, Sr2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.62 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 six TaO6 octahedra and faces with six equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–15°. There are a spread of Ta–O bond distances ranging from 1.91–2.10 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 6–16°. There are a spread of Ta–O bond distances ranging from 1.88–2.18 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Sr2+ and one Ta5+ atom to form distorted corner-sharing OSr3Ta tetrahedra. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Sr2+ and two Ta5+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Sr2+ and two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to three equivalent Sr2+ and two equivalent Ta5+ atoms. In the fifth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Ta5+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two Ta5+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Sr2+ and one Ta5+ atom.