Materials Data on Al2Si2O7 by Materials Project
Al2Si2O7 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one Al2Si2O7 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form distorted AlO4 trigonal pyramids that share corners with two SiO4 tetrahedra and edges with two equivalent AlO4 trigonal pyramids. There is two shorter (1.72 Å) and two longer (1.92 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form distorted AlO4 trigonal pyramids that share corners with two SiO4 tetrahedra and edges with two equivalent AlO4 trigonal pyramids. There are a spread of Al–O bond distances ranging from 1.72–1.92 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent SiO4 tetrahedra and corners with two AlO4 trigonal pyramids. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent SiO4 tetrahedra and corners with two AlO4 trigonal pyramids. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Al3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a water-like geometry to two Al3+ atoms. In the seventh O2- site, O2- is bonded in a water-like geometry to two Al3+ atoms.