Materials Data on Al2CrO5 by Materials Project
CrAl2O5 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with six AlO6 octahedra, and edges with four AlO6 octahedra. The corner-sharing octahedra tilt angles range from 46–61°. There are a spread of Cr–O bond distances ranging from 1.88–2.00 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form distorted AlO6 octahedra that share corners with three equivalent CrO6 octahedra, corners with four AlO6 octahedra, an edgeedge with one AlO6 octahedra, edges with two equivalent CrO6 octahedra, and a faceface with one AlO6 octahedra. The corner-sharing octahedra tilt angles range from 46–53°. There are a spread of Al–O bond distances ranging from 1.83–2.05 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form distorted AlO6 octahedra that share corners with three equivalent CrO6 octahedra, corners with four AlO6 octahedra, an edgeedge with one AlO6 octahedra, edges with two equivalent CrO6 octahedra, and a faceface with one AlO6 octahedra. The corner-sharing octahedra tilt angles range from 46–53°. There are a spread of Al–O bond distances ranging from 1.82–2.05 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr4+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded to one Cr4+ and three Al3+ atoms to form OAl3Cr trigonal pyramids that share corners with four OAl2Cr2 trigonal pyramids and edges with four OAl3Cr trigonal pyramids. In the third O2- site, O2- is bonded to one Cr4+ and three Al3+ atoms to form OAl3Cr trigonal pyramids that share corners with four OAl2Cr2 trigonal pyramids and edges with four OAl3Cr trigonal pyramids. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr4+ and two equivalent Al3+ atoms. In the fifth O2- site, O2- is bonded to two equivalent Cr4+ and two equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl2Cr2 trigonal pyramids. In the sixth O2- site, O2- is bonded to two equivalent Cr4+ and two equivalent Al3+ atoms to form distorted OAl2Cr2 trigonal pyramids that share corners with four OAl2Cr2 trigonal pyramids and edges with four OAl3Cr trigonal pyramids.