Materials Data on Na3Sr2Ti3(Si2O9)2 by Materials Project

Abstract

Na3Sr2Ti3(Si2O9)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded to six O atoms to form NaO6 octahedra that share corners with two equivalent SiO4 tetrahedra, corners with two equivalent TiO5 trigonal bipyramids, edges with two equivalent TiO6 octahedra, and edges with four NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.28–2.40 Å. In the second Na site, Na is bonded to six O atoms to form NaO6 octahedra that share corners with four equivalent SiO4 tetrahedra, corners with two equivalent TiO5 trigonal bipyramids, edges with two equivalent TiO6 octahedra, and edges with four equivalent NaO6 octahedra. There are two shorter (2.30 Å) and four longer (2.52 Å) Na–O bond lengths. Sr is bonded in a 11-coordinate geometry to eleven O atoms. There are a spread of Sr–O bond distances ranging from 2.72–3.20 Å. There are two inequivalent Ti sites. In the first Ti site, Ti is bonded to five O atoms to form distorted TiO5 trigonal bipyramids that share corners with three NaO6 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Ti–O bond distances ranging from 1.68–2.01 Å. In the second Ti site, Ti is bonded to six O atoms to form TiO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with six NaO6 octahedra. There is two shorter (1.85 Å) and four longer (2.07 Å) Ti–O bond length. Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one TiO6 octahedra, corners with two NaO6 octahedra, a cornercorner with one SiO4 tetrahedra, and corners with two equivalent TiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 54–64°. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. There are six inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two equivalent Sr, one Ti, and one Si atom. In the second O site, O is bonded to three Na and one Ti atom to form a mixture of distorted edge and corner-sharing ONa3Ti trigonal pyramids. In the third O site, O is bonded in a 1-coordinate geometry to two equivalent Na, one Sr, and one Ti atom. In the fourth O site, O is bonded in a 2-coordinate geometry to two equivalent Sr and two equivalent Si atoms. In the fifth O site, O is bonded in a 4-coordinate geometry to two equivalent Sr, one Ti, and one Si atom. In the sixth O site, O is bonded in a distorted rectangular see-saw-like geometry to two Na, one Ti, and one Si atom.