Materials Data on BaAl2(SiO4)2 by Materials Project

Abstract

BaAl2Si2O8 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ba2+ is bonded to twelve equivalent O2- atoms to form BaO12 cuboctahedra that share edges with six equivalent BaO12 cuboctahedra, edges with six equivalent AlO4 tetrahedra, and edges with six equivalent SiO4 tetrahedra. All Ba–O bond lengths are 3.16 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent SiO4 tetrahedra and edges with three equivalent BaO12 cuboctahedra. There is one shorter (1.72 Å) and three longer (1.77 Å) Al–O bond length. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four equivalent AlO4 tetrahedra and edges with three equivalent BaO12 cuboctahedra. There is one shorter (1.60 Å) and three longer (1.64 Å) Si–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Al3+ and one Si4+ atom.