DOE OSTI2020
Sm4Ti4S4O9 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded in a 9-coordinate geometry to four S2- and five O2- atoms. There are two shorter (2.94 Å) and two longer (2.98 Å) Sm–S bond lengths. There are a spread of Sm–O bond distances ranging from 2.39–2.65 Å. In the second Sm3+ site, Sm3+ is bonded in a 8-coordinate geometry to four S2- and four O2- atoms. There are two shorter (2.93 Å) and two longer (3.01 Å) Sm–S bond lengths. There are a spread of Sm–O bond distances ranging from 2.34–2.50 Å. In the third Sm3+ site, Sm3+ is bonded in a 9-coordinate geometry to three S2- and six O2- atoms. There are one shorter (2.91 Å) and two longer (2.97 Å) Sm–S bond lengths. There are a spread of Sm–O bond distances ranging from 2.38–2.58 Å. In the fourth Sm3+ site, Sm3+ is bonded in a 6-coordinate geometry to one S2- and six O2- atoms. The Sm–S bond length is 3.04 Å. There are a spread of Sm–O bond distances ranging from 2.36–2.57 Å. There are four inequivalent Ti+3.50+ sites. In the first Ti+3.50+ site, Ti+3.50+ is bonded to four S2- and two O2- atoms to form a mixture of distorted edge and corner-sharing TiS4O2 octahedra. The corner-sharing octahedral tilt angles are 21°. There are two shorter (2.55 Å) and two longer (2.58 Å) Ti–S bond lengths. There is one shorter (1.87 Å) and one longer (1.89 Å) Ti–O bond length. In the second Ti+3.50+ site, Ti+3.50+ is bonded to four S2- and two O2- atoms to form a mixture of distorted edge and corner-sharing TiS4O2 octahedra. The corner-sharing octahedral tilt angles are 21°. There are two shorter (2.51 Å) and two longer (2.61 Å) Ti–S bond lengths. There is one shorter (1.87 Å) and one longer (1.90 Å) Ti–O bond length. In the third Ti+3.50+ site, Ti+3.50+ is bonded to five O2- atoms to form a mixture of distorted edge and corner-sharing TiO5 trigonal bipyramids. There are a spread of Ti–O bond distances ranging from 1.88–2.12 Å. In the fourth Ti+3.50+ site, Ti+3.50+ is bonded to five O2- atoms to form a mixture of distorted edge and corner-sharing TiO5 trigonal bipyramids. There are a spread of Ti–O bond distances ranging from 1.85–2.13 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to three Sm3+ and two equivalent Ti+3.50+ atoms. In the second S2- site, S2- is bonded in a 2-coordinate geometry to three Sm3+ and two equivalent Ti+3.50+ atoms. In the third S2- site, S2- is bonded in a 2-coordinate geometry to two equivalent Sm3+ and two equivalent Ti+3.50+ atoms. In the fourth S2- site, S2- is bonded in a 2-coordinate geometry to four Sm3+ and two equivalent Ti+3.50+ atoms. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded to three Sm3+ and one Ti+3.50+ atom to form distorted OSm3Ti tetrahedra that share corners with two equivalent OSm3Ti tetrahedra, corners with two equivalent OSm2Ti2 trigonal pyramids, and edges with two equivalent OSm3Ti tetrahedra. In the second O2- site, O2- is bonded to three Sm3+ and one Ti+3.50+ atom to form distorted OSm3Ti tetrahedra that share corners with two equivalent OSm3Ti tetrahedra, corners with two equivalent OSm2Ti2 trigonal pyramids, edges with two equivalent OSm3Ti tetrahedra, and an edgeedge with one OSm2Ti2 trigonal pyramid. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sm3+ and two Ti+3.50+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Sm3+ and two Ti+3.50+ atoms to form distorted OSm2Ti2 trigonal pyramids that share corners with six OSm3Ti tetrahedra, corners with two equivalent OSm2Ti2 trigonal pyramids, and an edgeedge with one OSm3Ti tetrahedra. In the fifth O2- site, O2- is bonded to three Sm3+ and one Ti+3.50+ atom to form distorted OSm3Ti tetrahedra that share corners with two equivalent OSm3Ti tetrahedra, a cornercorner with one OSm2Ti2 trigonal pyramid, and edges with two equivalent OSm3Ti tetrahedra. In the sixth O2- site, O2- is bonded to three Sm3+ and one Ti+3.50+ atom to form distorted OSm3Ti tetrahedra that share corners with two equivalent OSm3Ti tetrahedra, a cornercorner with one OSm2Ti2 trigonal pyramid, and edges with two equivalent OSm3Ti tetrahedra. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two Sm3+ and two equivalent Ti+3.50+ atoms. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two Sm3+ and two equivalent Ti+3.50+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one Sm3+ and two Ti+3.50+ atoms.