Materials Data on CaAl2O12 by Materials Project
CaO7Al2O3O2 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional and consists of two hexaoxane molecules and one CaO7Al2O3 framework. In the CaO7Al2O3 framework, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.28–2.85 Å. Al is bonded to four O atoms to form a mixture of distorted corner and edge-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.76–1.80 Å. There are six inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Al atoms. In the second O site, O is bonded in a 2-coordinate geometry to one Ca and two equivalent Al atoms. In the third O site, O is bonded in a water-like geometry to one Ca and one O atom. The O–O bond length is 1.26 Å. In the fourth O site, O is bonded in a distorted T-shaped geometry to two equivalent Ca and one Al atom. In the fifth O site, O is bonded in a distorted trigonal non-coplanar geometry to one Ca and two equivalent O atoms. Both O–O bond lengths are 1.61 Å. In the sixth O site, O is bonded in a water-like geometry to two O atoms.