Materials Data on BaSi4O9 by Materials Project
BaSi4O9 crystallizes in the hexagonal P-6c2 space group. The structure is three-dimensional. Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are six shorter (2.80 Å) and six longer (3.32 Å) Ba–O bond lengths. 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 two equivalent SiO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. 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 six equivalent O2- atoms to form corner-sharing SiO6 octahedra. All Si–O bond lengths are 1.80 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+ and two equivalent Si4+ atoms.