Materials Data on La4Al2O9 by Materials Project

Abstract

La4Al2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.39–2.76 Å. In the second La3+ site, La3+ is bonded to six O2- atoms to form LaO6 octahedra that share corners with five AlO4 tetrahedra. There are a spread of La–O bond distances ranging from 2.40–2.51 Å. In the third La3+ site, La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.34–2.82 Å. In the fourth La3+ site, La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.41–2.85 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent LaO6 octahedra and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–67°. There is two shorter (1.77 Å) and two longer (1.79 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent LaO6 octahedra and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–67°. All Al–O bond lengths are 1.78 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two La3+ and one Al3+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the sixth O2- site, O2- is bonded to four La3+ atoms to form a mixture of edge and corner-sharing OLa4 tetrahedra. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two La3+ and two Al3+ atoms. In the eighth O2- site, O2- is bonded to four La3+ atoms to form a mixture of edge and corner-sharing OLa4 tetrahedra. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom.