DOE OSTI2020
TiOsSi crystallizes in the orthorhombic Ima2 space group. The structure is three-dimensional. there are three inequivalent Ti3+ sites. In the first Ti3+ site, Ti3+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of Ti–Si bond distances ranging from 2.62–2.93 Å. In the second Ti3+ site, Ti3+ is bonded to five Si4- atoms to form distorted TiSi5 square pyramids that share corners with six OsSi4 tetrahedra, corners with five equivalent TiSi5 trigonal bipyramids, edges with two equivalent TiSi5 square pyramids, edges with six OsSi4 tetrahedra, and edges with two equivalent TiSi5 trigonal bipyramids. There are three shorter (2.63 Å) and two longer (2.64 Å) Ti–Si bond lengths. In the third Ti3+ site, Ti3+ is bonded to five Si4- atoms to form TiSi5 trigonal bipyramids that share corners with five equivalent TiSi5 square pyramids, corners with six OsSi4 tetrahedra, edges with two equivalent TiSi5 square pyramids, edges with six OsSi4 tetrahedra, and edges with two equivalent TiSi5 trigonal bipyramids. There are four shorter (2.64 Å) and one longer (2.68 Å) Ti–Si bond lengths. There are two inequivalent Os1+ sites. In the first Os1+ site, Os1+ is bonded to four Si4- atoms to form OsSi4 tetrahedra that share corners with two equivalent TiSi5 square pyramids, corners with ten OsSi4 tetrahedra, corners with two equivalent TiSi5 trigonal bipyramids, edges with two equivalent TiSi5 square pyramids, edges with two equivalent OsSi4 tetrahedra, and edges with two equivalent TiSi5 trigonal bipyramids. There are two shorter (2.48 Å) and two longer (2.49 Å) Os–Si bond lengths. In the second Os1+ site, Os1+ is bonded to four Si4- atoms to form OsSi4 tetrahedra that share corners with two equivalent TiSi5 square pyramids, corners with ten OsSi4 tetrahedra, corners with two equivalent TiSi5 trigonal bipyramids, edges with two equivalent TiSi5 square pyramids, edges with two OsSi4 tetrahedra, and edges with two equivalent TiSi5 trigonal bipyramids. There are one shorter (2.41 Å) and three longer (2.47 Å) Os–Si bond lengths. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 10-coordinate geometry to three Ti3+ and six Os1+ atoms. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to six Ti3+ and three Os1+ atoms.