Materials Data on Sm4Al2O9 by Materials Project

Sm4Al2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded to six O2- atoms to form SmO6 octahedra that share corners with five AlO4 tetrahedra and edges with two equivalent SmO7 hexagonal pyramids. There are a spread of Sm–O bond distances ranging from 2.30–2.44 Å. In the second Sm3+ site, Sm3+ is bonded to seven O2- atoms to form distorted SmO7 hexagonal pyramids that share corners with three AlO4 tetrahedra, edges with two equivalent SmO6 octahedra, and edges with two AlO4 tetrahedra. There are a spread of Sm–O bond distances ranging from 2.30–2.57 Å. In the third Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.32–2.73 Å. In the fourth Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.34–2.83 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 SmO7 hexagonal pyramids, corners with two equivalent SmO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one SmO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 38–52°. 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 SmO7 hexagonal pyramid, corners with three equivalent SmO6 octahedra, a cornercorner with one AlO4 tetrahedra, and an edgeedge with one SmO7 hexagonal pyramid. The corner-sharing octahedra tilt angles range from 48–62°. 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 4-coordinate geometry to three Sm3+ and one Al3+ atom. In the second O2- site, O2- is bonded to four Sm3+ atoms to form OSm4 tetrahedra that share corners with four OSm3Al tetrahedra and edges with two OSm4 tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Sm3+ and one Al3+ atom. In the fourth O2- site, O2- is bonded to three Sm3+ and one Al3+ atom to form distorted corner-sharing OSm3Al tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Sm3+ and two Al3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Sm3+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three Sm3+ and one Al3+ atom. In the eighth O2- site, O2- is bonded to four Sm3+ atoms to form a mixture of edge and corner-sharing OSm4 tetrahedra. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Sm3+ and one Al3+ atom.