Materials Data on Al2O3 by Materials Project

Abstract

Al2O3 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent AlO5 trigonal bipyramids and edges with six equivalent AlO6 octahedra. There is three shorter (1.98 Å) and three longer (2.01 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with six equivalent AlO6 octahedra and corners with six equivalent AlO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 61–62°. There are a spread of Al–O bond distances ranging from 1.75–1.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three equivalent Al3+ atoms. In the second O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 tetrahedra. In the third O2- site, O2- is bonded to four Al3+ atoms to form a mixture of edge and corner-sharing OAl4 tetrahedra.