DOI: 10.17188/1264857
title: Materials Data on Y4Al2O9 by Materials Project

description: Y4Al2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six O2- atoms to form distorted YO6 octahedra that share a cornercorner with one YO7 hexagonal pyramid, corners with two equivalent YO6 octahedra, corners with three AlO4 tetrahedra, an edgeedge with one YO7 hexagonal pyramid, and edges with two YO6 octahedra. The corner-sharing octahedra tilt angles range from 55–71°. There are a spread of Y–O bond distances ranging from 2.26–2.37 Å. In the second Y3+ site, Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.28–2.63 Å. In the third Y3+ site, Y3+ is bonded to six O2- atoms to form YO6 octahedra that share corners with two equivalent YO6 octahedra, corners with five AlO4 tetrahedra, edges with two equivalent YO7 hexagonal pyramids, and an edgeedge with one YO6 octahedra. The corner-sharing octahedra tilt angles range from 55–71°. There are a spread of Y–O bond distances ranging from 2.23–2.38 Å. In the fourth Y3+ site, Y3+ is bonded to seven O2- atoms to form distorted YO7 hexagonal pyramids that share a cornercorner with one YO6 octahedra, corners with three AlO4 tetrahedra, edges with three YO6 octahedra, and edges with two AlO4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. There are a spread of Y–O bond distances ranging from 2.27–2.55 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 two equivalent YO7 hexagonal pyramids, corners with four YO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one YO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 39–74°. There are a spread of Al–O bond distances ranging from 1.76–1.78 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one YO7 hexagonal pyramid, corners with four YO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one YO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 45–62°. There are a spread of Al–O bond distances ranging from 1.75–1.78 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Y3+ and one Al3+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Y3+ and one Al3+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Y3+ and one Al3+ atom. In the fourth O2- site, O2- is bonded to two Y3+ and two Al3+ atoms to form a mixture of distorted edge and corner-sharing OY2Al2 tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Y3+ and one Al3+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Y3+ and one Al3+ atom. In the seventh O2- site, O2- is bonded to three Y3+ and one Al3+ atom to form a mixture of distorted edge and corner-sharing OY3Al tetrahedra. In the eighth O2- site, O2- is bonded to four Y3+ atoms to form a mixture of edge and corner-sharing OY4 tetrahedra. In the ninth O2- site, O2- is bonded to four Y3+ atoms to form OY4 tetrahedra that share corners with five OY2Al2 tetrahedra and edges with two OY4 tetrahedra.