Materials Data on Ca2AlSi2O7 by Materials Project
Ca2AlSi2O7 crystallizes in the tetragonal P-42_1m space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.48–2.82 Å. Al is bonded to four equivalent O atoms to form AlO4 tetrahedra that share corners with four equivalent SiO4 tetrahedra. All Al–O bond lengths are 1.80 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with two equivalent AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.70 Å. There are three inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two equivalent Ca and two equivalent Si atoms. In the second O site, O is bonded in a 2-coordinate geometry to two equivalent Ca, one Al, and one Si atom. In the third O site, O is bonded to three equivalent Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si tetrahedra.