Materials Data on SrGd2Al2O7 by Materials Project

Abstract

Gd2SrAl2O7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. 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 AlO6 octahedra. There are four shorter (2.65 Å) and eight longer (2.79 Å) Sr–O bond lengths. Gd3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Gd–O bond distances ranging from 2.27–2.68 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with five equivalent AlO6 octahedra and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Al–O bond distances ranging from 1.88–2.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Sr2+, two equivalent Gd3+, and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a 6-coordinate geometry to five equivalent Gd3+ and one Al3+ atom. In the third O2- site, O2- is bonded to four equivalent Sr2+ and two equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OSr4Al2 octahedra. The corner-sharing octahedral tilt angles are 0°.