Materials Data on Eu4Al2O9 by Materials Project
Eu4Al2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Eu3+ sites. In the first Eu3+ site, Eu3+ is bonded to six O2- atoms to form EuO6 octahedra that share corners with five AlO4 tetrahedra and edges with two equivalent EuO7 hexagonal pyramids. There are a spread of Eu–O bond distances ranging from 2.29–2.45 Å. In the second Eu3+ site, Eu3+ is bonded to seven O2- atoms to form distorted EuO7 hexagonal pyramids that share corners with three AlO4 tetrahedra, edges with two equivalent EuO6 octahedra, and edges with two AlO4 tetrahedra. There are a spread of Eu–O bond distances ranging from 2.33–2.61 Å. In the third Eu3+ site, Eu3+ is bonded in a 8-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.34–2.74 Å. In the fourth Eu3+ site, Eu3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.33–2.86 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 EuO7 hexagonal pyramid, corners with three equivalent EuO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one EuO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 48–61°. There are a spread of Al–O bond distances ranging from 1.75–1.78 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent EuO7 hexagonal pyramids, corners with two equivalent EuO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one EuO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 38–50°. There are a spread of Al–O bond distances ranging from 1.76–1.78 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Eu3+ and one Al3+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Eu3+ and one Al3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Eu3+ and one Al3+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Eu3+ and two Al3+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Eu3+ and one Al3+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Eu3+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three Eu3+ and one Al3+ atom. In the eighth O2- site, O2- is bonded to four Eu3+ atoms to form a mixture of edge and corner-sharing OEu4 tetrahedra. In the ninth O2- site, O2- is bonded to four Eu3+ atoms to form a mixture of edge and corner-sharing OEu4 tetrahedra.