Materials Data on Be3Al2Si6O19 by Materials Project
(Be3Al2Si6O18)2O2 crystallizes in the hexagonal P6/mcc space group. The structure is three-dimensional and consists of two water molecules and one Be3Al2Si6O18 framework. In the Be3Al2Si6O18 framework, Be is bonded in a distorted rectangular see-saw-like geometry to four equivalent O atoms. All Be–O bond lengths are 1.66 Å. Al is bonded to six equivalent O atoms to form AlO6 octahedra that share corners with six equivalent SiO4 tetrahedra. All Al–O bond lengths are 1.92 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent AlO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Si–O bond distances ranging from 1.61–1.64 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to one Be, one Al, and one Si atom. In the second O site, O is bonded in a linear geometry to two equivalent Si atoms.