Materials Data on Ca3Al2(SiO6)2 by Materials Project
Ca3Al2(SiO6)2 crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.27 Å) and four longer (2.68 Å) Ca–O bond lengths. In the second Ca site, Ca is bonded in a distorted body-centered cubic geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.54 Å. Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.84–2.04 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with four equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 39–42°. There is two shorter (1.66 Å) and two longer (1.67 Å) Si–O bond length. There are three inequivalent O sites. In the first O site, O is bonded to two equivalent Ca, one Al, and one Si atom to form a mixture of distorted edge and corner-sharing OCa2AlSi trigonal pyramids. In the second O site, O is bonded in a trigonal non-coplanar geometry to two Ca and one Al atom. In the third O site, O is bonded in a 4-coordinate geometry to two Ca, one Al, and one Si atom.