DOI: 10.17188/1204117
title: Materials Data on CaAl2O4 by Materials Project

description: CaAl2O4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.34 Å. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.75 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with ten AlO4 tetrahedra and an edgeedge with one AlO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.32–2.71 Å. There are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. There is three shorter (1.77 Å) and one longer (1.79 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–56°. There is two shorter (1.77 Å) and two longer (1.79 Å) Al–O bond length. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 60–75°. There are a spread of Al–O bond distances ranging from 1.76–1.78 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one CaO6 octahedra, corners with four AlO4 tetrahedra, and an edgeedge with one CaO6 octahedra. The corner-sharing octahedral tilt angles are 62°. There is three shorter (1.77 Å) and one longer (1.79 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–72°. There is one shorter (1.77 Å) and three longer (1.78 Å) Al–O bond length. In the sixth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–66°. There is three shorter (1.77 Å) and one longer (1.78 Å) Al–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Al3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Al3+ atoms. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and two Al3+ atoms. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+ and two Al3+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+ and two Al3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to two Ca2+ and two Al3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Al3+ atoms.