DOE OSTI2020
Sm2TiO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded to seven O2- atoms to form distorted SmO7 pentagonal bipyramids that share corners with two equivalent SmO7 hexagonal pyramids, corners with three equivalent TiO5 trigonal bipyramids, edges with three equivalent SmO7 hexagonal pyramids, edges with two equivalent SmO7 pentagonal bipyramids, and edges with two equivalent TiO5 trigonal bipyramids. There are a spread of Sm–O bond distances ranging from 2.34–2.45 Å. In the second Sm3+ site, Sm3+ is bonded to seven O2- atoms to form distorted SmO7 hexagonal pyramids that share corners with two equivalent SmO7 pentagonal bipyramids, a cornercorner with one TiO5 trigonal bipyramid, edges with four equivalent SmO7 hexagonal pyramids, edges with three equivalent SmO7 pentagonal bipyramids, and edges with two equivalent TiO5 trigonal bipyramids. There are a spread of Sm–O bond distances ranging from 2.39–2.42 Å. Ti4+ is bonded to five O2- atoms to form distorted TiO5 trigonal bipyramids that share a cornercorner with one SmO7 hexagonal pyramid, corners with three equivalent SmO7 pentagonal bipyramids, corners with two equivalent TiO5 trigonal bipyramids, edges with two equivalent SmO7 hexagonal pyramids, and edges with two equivalent SmO7 pentagonal bipyramids. There are a spread of Ti–O bond distances ranging from 1.79–2.00 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to four Sm3+ atoms to form a mixture of corner and edge-sharing OSm4 tetrahedra. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sm3+ and one Ti4+ atom. In the third O2- site, O2- is bonded to three Sm3+ and one Ti4+ atom to form distorted OSm3Ti tetrahedra that share corners with nine OSm4 tetrahedra and edges with five OSm3Ti tetrahedra. In the fourth O2- site, O2- is bonded to two Sm3+ and two equivalent Ti4+ atoms to form distorted OSm2Ti2 tetrahedra that share corners with six OSm4 tetrahedra and edges with five OSm3Ti tetrahedra. In the fifth O2- site, O2- is bonded to three Sm3+ and one Ti4+ atom to form OSm3Ti tetrahedra that share corners with nine OSm4 tetrahedra and edges with four OSm3Ti tetrahedra.