Materials Data on La2Ti2SiO9 by Materials Project
La2Ti2SiO9 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 7-coordinate geometry to eight O2- atoms. There are a spread of La–O bond distances ranging from 2.39–2.99 Å. In the second La3+ site, La3+ is bonded in a 1-coordinate geometry to ten O2- atoms. There are a spread of La–O bond distances ranging from 2.25–3.01 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with two equivalent SiO4 tetrahedra, and edges with two equivalent TiO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Ti–O bond distances ranging from 1.90–2.02 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with two equivalent TiO6 octahedra, a cornercorner with one SiO4 tetrahedra, and an edgeedge with one TiO6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Ti–O bond distances ranging from 1.89–2.32 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three TiO6 octahedra. The corner-sharing octahedra tilt angles range from 27–57°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two La3+, one Ti4+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Ti4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three La3+, one Ti4+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a linear geometry to one La3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ti4+ atoms. In the sixth O2- site, O2- is bonded in a distorted L-shaped geometry to two La3+ and two equivalent Ti4+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent La3+ and two equivalent Ti4+ atoms.