Materials Data on La3(Al2Si3)2 by Materials Project

Abstract

La3(Al2Si3)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are two inequivalent La sites. In the first La site, La is bonded in a 12-coordinate geometry to nine Si atoms. There are a spread of La–Si bond distances ranging from 3.14–3.23 Å. In the second La site, La is bonded to six equivalent Si atoms to form distorted LaSi6 octahedra that share corners with twelve AlSi4 tetrahedra, edges with six equivalent LaSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All La–Si bond lengths are 3.10 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to four Si atoms to form AlSi4 tetrahedra that share corners with three equivalent LaSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. There are three shorter (2.52 Å) and one longer (2.58 Å) Al–Si bond lengths. In the second Al site, Al is bonded to four Si atoms to form AlSi4 tetrahedra that share corners with three equivalent LaSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent LaSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedral tilt angles are 22°. There are three shorter (2.52 Å) and one longer (2.54 Å) Al–Si bond lengths. There are three inequivalent Si sites. In the first Si site, Si is bonded to three equivalent La and four Al atoms to form a mixture of distorted corner and edge-sharing SiLa3Al4 pentagonal bipyramids. In the second Si site, Si is bonded in a 9-coordinate geometry to six equivalent La and three equivalent Si atoms. All Si–Si bond lengths are 2.43 Å. In the third Si site, Si is bonded in a 7-coordinate geometry to three equivalent La and four Al atoms.