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 to six O2- atoms to form LaO6 octahedra that share corners with five AlO4 tetrahedra and edges with two equivalent LaO7 hexagonal pyramids. There are a spread of La–O bond distances ranging from 2.39–2.52 Å. In the second 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 2.42–2.90 Å. In the third La3+ site, La3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of La–O bond distances ranging from 2.41–3.07 Å. In the fourth La3+ site, La3+ is bonded to seven O2- atoms to form distorted LaO7 hexagonal pyramids that share corners with three AlO4 tetrahedra, edges with two equivalent LaO6 octahedra, and edges with two AlO4 tetrahedra. There are a spread of La–O bond distances ranging from 2.36–2.67 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 a cornercorner with one LaO7 hexagonal pyramid, corners with three equivalent LaO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one LaO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 45–62°. 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 LaO7 hexagonal pyramids, corners with two equivalent LaO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one LaO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 36–50°. There is two shorter (1.78 Å) and two longer (1.79 Å) Al–O bond length. 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 2-coordinate geometry to two La3+ and two Al3+ atoms. In the third O2- site, O2- is bonded to four La3+ atoms to form a mixture of corner and edge-sharing OLa4 tetrahedra. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the fifth O2- site, O2- is bonded to four La3+ atoms to form a mixture of corner and edge-sharing OLa4 tetrahedra. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to three La3+ and one Al3+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Al3+ atom.