Materials Data on CaAl2O4 by Materials Project
CaAl2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.50 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Al–O bond distances ranging from 1.93–2.01 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Al–O bond distances ranging from 1.91–1.98 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ca2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ca2+ and three Al3+ atoms. In the third O2- site, O2- is bonded to two equivalent Ca2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Al3 square pyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ca2+ and three Al3+ atoms.